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ANALYSIS OF PERMIT VEHICLES IN RHODE ISLAND
BY
SARJU MULMI
A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
IN
CIVIL & ENVIRONMENTAL ENGINEERING
UNIVERSITY OF RHODE ISLAND
2011
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MASTER OF SCIENCE THESIS
OF
SARJU MULMI
APPROVED:
Thesis Committee:
Major Professor: Prof. Mayrai Gindy
Prof. Valerie Maier-Speredelozzi
Prof. Martin Sadd
Prof. George Tsiatas
Nasser H. Zawia
DEAN OF THE GRADUATE SCHOOL
UNIVERSITY OF RHODE ISLAND
2011
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may not elect to make adjustments to the current load rating standard permit vehicle or
their permit review process.
The study shows that a data quality check should be set up at the onset of the
permit application process to get error-free, valid truck information from the database.
There is also a need to establish a set of guidelines to be followed to forward the
permit applications of overweight trucks to RIDOT for detailed and in-depth review.
The 3- and 4-axle permit trucks were found to be the critical trucks in terms of load
effects on the bridges with the effect being more severe in the case of short-span
bridges.
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ACKNOWLEDGMENTS
First and foremost, I would like to extend my gratitude to Prof. Dr. Mayrai Gindy
for her constant support and guidance during the course of my work. I would like to
give special thanks to Prof. Dr. George Tsiatas for his help and advice during my stay
at URI. I would also like to thank the members of my committee, Prof. Dr. Martin
Sadd and Prof. Dr. Valerie Maier-Speredelozzi for helping review and provide
insightful feedback on the content of this thesis. I would like to thank Rhode Island
Department of Transportation for providing the funding for the research, especially
Dave Morgan, Thomas Viall, Keith Gaulin and Mike Sock for providing various
research materials and for their feedbacks. I am also thankful to faculty and staffs of
the Department of Civil and Environmental engineering for their help and support.
Finally, I would like to thank my family and friends for their continued support
throughout this research.
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TABLE OF CONTENTS
ABSTRACT................................................................................................................... ii!
ACKNOWLEDGMENTS ............................................................................................ iv!
TABLE OF CONTENTS............................................................................................... v!
LIST OF TABLES ...................................................................................................... viii!
LIST OF FIGURES ....................................................................................................... x!
CHAPTER 1 .................................................................................................................. 1!
1.1 History of Federal and State Weight Regulations................................................ 4!
1.1.1 The Federal Aid Highway Act of 1956 ............................................................. 5!
1.1.2 The Federal Aid Highway Act Amendments of 1974....................................... 6!
1.1.3 The Surface Transportation Assistance Act (STAA) of 1982........................... 7!
1.1.4 The Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991........ 8!
1.2 Objectives ........................................................................................................... 10!
CHAPTER 2 ................................................................................................................ 13!
2.1 Single-Trip Oversize/Overweight Vehicle Permit Database.............................. 16!
2.1.1 Data Quality Checks........................................................................................ 16!
2.1.2 Vehicle Size and Weight Classification .......................................................... 18!
2.2 Characteristics of Overweight Vehicles ............................................................. 22!
2.2.1 Number of Permit Applications....................................................................... 22!
2.2.2 Number of Permit Re-Submittals .................................................................... 24!
2.2.3 Time Required to Review Permits .................................................................. 26!
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2.2.4 Requested Travel Route .................................................................................. 29!
2.2.5 Number of Axles ............................................................................................. 30!
2.2.6 Gross Vehicle Weight...................................................................................... 31!
2.3 Criteria for Requiring a RIDOT Review............................................................ 34!
2.3.1 Size Characteristics ......................................................................................... 34!
2.3.2 Weight Characteristics..................................................................................... 38!
2.4 Load Effects of Overweight Vehicles ................................................................ 39!
CHAPTER 3 ................................................................................................................ 47!
3.1 Vehicle Body Types ........................................................................................... 49!
3.2 Comparison of RI Body Types with Previous Studies....................................... 59!
CHAPTER 4 ................................................................................................................ 63!
4.1 Rhode Island Standard Permit Vehicles ............................................................. 74!
4.2 Load Effects Normalized to RI Standard Permit Trucks.................................... 81!
4.3 Proposed New Standard Permit Vehicles........................................................... 98!
4.4 Analysis for Additional Standard Trucks ......................................................... 106!
CHAPTER 5 .............................................................................................................. 127!
APPENDIX A: DATA QUALITY CHECK ............................................................. 132!
APPENDIX B: WEIGHT LIMIT VIOLATIONS..................................................... 133!
APPENDIX C: PERMIT PROCESSING TIME AND LOAD EFFECTS................ 136!
APPENDIX D: NEW JERSEY BODY TYPE ORIGINAL.................................... 147!
APPENDIX E: NEW JERSEY BODY TYPE REVISED...................................... 150!
APPENDIX F: CALTRAN BODY TYPE ORIGINAL ......................................... 153!
APPENDIX G: CALTRAN BODY TYPE REVISED........................................... 156!
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BIBLIOGRAPHY...................................................................................................... 159!
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LIST OF TABLES
Table 1-1 Current Federal and State Size and Weight Regulations............................... 9!
Table 1-2 Historical Development of Overweight Vehicles.......................................... 9!
Table 2-1 NETC Envelope Vehicle Configurations for Non-divisible Single-Trip
Permits (NETC, 1995) ................................................................................................. 15!
Table 2-2 Parameter Definition for the RI OS/OW Vehicle Permit Database ............ 17!
Table 2-3 Data Quality Checks .................................................................................... 18!
Table 2-4 Legal Size and Weight Limits Exceeded..................................................... 20!
Table 2-5 Vehicle size and weight classification by agency........................................ 22!
Table 2-6 Number of Application Submittals by Agency for Overweight Vehicles... 25!
Table 2-7 Time Required to Review Overweight Permits by Agency and Number of
Submittals..................................................................................................................... 28!
Table 2-8 Statistical Parameters for the Time Required to Review Overweight Permits
by Agency .................................................................................................................... 28!
Table 2-9 Statistical Parameters of GVW for Different Number of Axles.................. 33!
Table 2-10 Strictly Oversize Vehicles ......................................................................... 35!
Table 2-11 Approximate Normal Statistical Parameters of Positive Moment............. 42!
Table 2-12 Approximate Normal Statistical Parameters of Negative Moment ........... 43!
Table 2-13 Approximate Normal Statistical Parameters of Shear ............................... 43!
Table 2-14 Table of Probability of Exceedance of HL93 Load Effects ...................... 45!
Table 3-1 FHWA Vehicle Classification (Traffic Monitoring Guide, 2001) .............. 48!
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Table 3-2 New Jersey Vehicle Body Type (International Road Dynamics Inc, 1999) 50!
Table 3-3 Caltrans Vehicle Body Type (Lu et al., 2002)............................................. 51!
Table 3-4 Original and Revised Body Types............................................................... 56!
Table 3-5 Most Frequent Body Types ......................................................................... 58!
Table 3-6 Comparison of RI Body Types with Preziosos Body Types...................... 62!
Table 4-1 Contribution of Truck Load in HL-93 for Positive Moment (kip-ft) .......... 66!
Table 4-2 Contribution of Truck Load in HL-93 for Negative Moment (kip-ft)......... 66!
Table 4-3 Contribution of Truck Load in HL-93 for Shear (kips)............................... 67!
Table 4-4 Approximate Normal Statistics of HL-93 Normalized Positive Moment ... 71!
Table 4-5 Approximate Normal Statistics of HL-93 Normalized Negative Moment.. 72!
Table 4-6 Approximate Normal Statistics of HL-93 Normalized Shear...................... 72!
Table 4-7 Difference Between RI Standard Vehicles and HL-93-Positive Moment... 78!
Table 4-8 Difference Between RI Standard Vehicles and HL-93-Negative Moment . 79!
Table 4-9 Difference Between RI Standard Vehicles and HL-93-Shear ..................... 79!
Table 4-10 Load Effects due to RI Standard Vehicles Positive Moment (kip-ft)..... 79!
Table 4-11 Effects due to RI Standard Vehicles Negative Moment (kip-ft) ............ 80!
Table 4-12 Effects due to RI Standard Vehicles Shear (kips) .................................. 80!
Table 4-13 Distribution of Number of Axles in Overweight Permit Vehicles ............ 81!
Table 4-14 Summary of Load Effect Ratios Normalized by RI Standard Trucks....... 98!
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LIST OF FIGURES
Figure 1.1 Number of Overweight/Overwidth Permits Issued by States....................... 2!
Figure 1.2 Overweight Permits Issued by States ........................................................... 3!
Figure 2.1 RI Legal Size Limits................................................................................... 21!
Figure 2.2 RI Legal Weight Limits .............................................................................. 21!
Figure 2.3 Monthly Variation of Overweight Permits Approved by Each Agency..... 23!
Figure 2.4 Number of Submittals for Each Agency..................................................... 26!
Figure 2.5 Time Required to Review Overweight Permits by Agency ....................... 27!
Figure 2.6 Statistical Variation of the Time Required to Review Overweight Permits
with the Number of Permit Re-submittals ................................................................... 29!
Figure 2.7 Requested Origin-Destination States for Overweight Permit Vehicles...... 30!
Figure 2.8 Variation of Number of Axles for Overweight Vehicles............................ 31!
Figure 2.9 CDF of GVW of Overweight Vehicles by Number of Axles..................... 32!
Figure 2.10 Seasonal Variation of GVW ..................................................................... 33!
Figure 2.11 Variation of Number of Axles for All Permit Vehicles............................ 34!
Figure 2.12 Width of Strictly OW Vehicles ................................................................ 36!
Figure 2.13 Height of Strictly OS Vehicles ................................................................. 37!
Figure 2.14 Width of Strictly Overwidth Vehicles...................................................... 37!
Figure 2.15 GVW of Strictly OW Vehicles ................................................................. 39!
Figure 2.16 Positive Moment for Short, Medium and Long Span by Agency ............ 41!
Figure 2.17 Negative Moment for Short, Medium and Long Span by Agency........... 41!
Figure 2.18 Shear for Short, Medium and Long Span by Agency............................... 42!
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Figure 2.19 Probability of Exceedance of Load Effects by Agency............................ 45!
Figure 2.20 Average and Maximum Load Effects for All Spans by Agency.............. 46!
Figure 3.1 Original and Revised New Jersey Body Types .......................................... 54!
Figure 3.2 Original and Revised Caltrans Body Types ............................................... 55!
Figure 3.3 FHWA Classification ................................................................................. 59!
Figure 4.1 HL-93 Loadings.......................................................................................... 65!
Figure 4.2 Positive Moment Ratio Normalized by HL-93........................................... 69!
Figure 4.3 Negative Moment Ratio Normalized by HL-93 ......................................... 70!
Figure 4.4 Shear Ratio Normalized by HL-93............................................................. 71!
Figure 4.5 Statistical Parameter of Positive Moment Ratio......................................... 72!
Figure 4.6 Statistical Parameter of Negative Moment Ratio ....................................... 73!
Figure 4.7 Statistical Parameter of Shear Ratio ........................................................... 73!
Figure 4.8 RI Standard Permit Vehicles ...................................................................... 76!
Figure 4.9 Difference Between RI Standard Vehicles and HL-93-Positive Moment.. 77!
Figure 4.10 Difference Between RI Standard Vehicles and HL-93-Negative Moment
...................................................................................................................................... 77!
Figure 4.11 Difference Between RI Standard Vehicles and HL-93-Shear .................. 78!
Figure 4.12 Load Effects of 3-axle Overweight Permit Vehicles Normalized by RI-
BP1 (a) Positive Moment (b) Negative Moment (c) Shear.......................................... 83!
Figure 4.13 Load Effects of 4-axle Overweight Permit Vehicles Normalized by RI-
BP2 (a) Positive Moment (b) Negative Moment (c) Shear.......................................... 86!
Figure 4.14 Load Effects of 5-axle Overweight Permit Vehicles Normalized by RI-
OP1 (a) Positive Moment (b) Negative Moment (c) Shear ......................................... 89!
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Figure 4.15 Load Effects of 6-axle Overweight Permit Vehicles Normalized by RI-
OP2 (a) Positive Moment (b) Negative Moment (c) Shear ......................................... 92!
Figure 4.16 Load Effects of 8-axle Overweight Permit Vehicles Normalized by RI-
OP3 (a) Positive Moment (b) Negative Moment (c) Shear ......................................... 95!
Figure 4.17 Revised 3- and 4-axle RI Standard Permit Vehicle.................................. 99!
Figure 4.18 Positive Moment of 3-axle Overweight Permit Vehicles Normalized by
RI-BP1R..................................................................................................................... 100!
Figure 4.19 Negative Moment of 3-axle Overweight Permit Vehicles Normalized by
RI-BP1R..................................................................................................................... 101!
Figure 4.20 Shear of 3-axle Overweight Permit Vehicles Normalized by RI-BP1R. 102!
Figure 4.21 Positive Moment of 4-axle Overweight Permit Vehicles Normalized by
RI-BP2R..................................................................................................................... 103!
Figure 4.22 Negative Moment of 4-axle Overweight Permit Vehicles Normalized by
RI-BP2R..................................................................................................................... 104!
Figure 4.23 Shear of 4-axle Overweight Permit Vehicles Normalized by RI-BP2R. 105!
Figure 4.24 Probability of Exceedance of 3-axle RI Standard Permit Truck ............ 105!
Figure 4.25 Probability of Exceedance of 4-axle RI Standard Permit Truck ............ 106!
Figure 4.26 AASHTO Legal loads for SHVs ............................................................ 107!
Figure 4.27 RI Blanket Permit Vehicles .................................................................... 107!
Figure 4.28 Load Effects of 4-axle Overweight Permit Vehicles Normalized by SU4
(a) Positive Moment (b) Negative Moment (c) Shear................................................ 108!
Figure 4.29 Load Effects of 5-axle Overweight Permit Vehicles Normalized by SU5
(a) Positive Moment (b) Negative Moment (c) Shear................................................ 111!
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Figure 4.30 Load Effects of 6-axle Overweight Permit Vehicles Normalized by SU6
(a) Positive Moment (b) Negative Moment (c) Shear................................................ 114!
Figure 4.31 Load Effects of 7-axle Overweight Permit Vehicles Normalized by SU7
(a) Positive Moment (b) Negative Moment (c) Shear................................................ 117!
Figure 4.32 Load Effects of 5-axle Overweight Permit Vehicles Normalized by RI-
BP3 (a) Positive Moment (b) Negative Moment (c) Shear........................................ 120!
Figure 4.33 Load Effects of 6-axle Overweight Permit Vehicles Normalized by RI-
BP4 (a) Positive Moment (b) Negative Moment (c) Shear........................................ 123!
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CHAPTER 1INTRODUCTION
Federal and State size and weight limit restrictions on heavy and large vehicles
have been established in the past and continued into the present to reduce the adverse
effect on highway bridges due to their passage. Any commercial vehicle exceeding the
legal size and/or weight limits is required to apply for and obtain a permit prior to its
travel. Currently, in the state of Rhode Island all permit applications are submitted
online to RIDMV via the RI.govs online application system.
Transport by trucks on the nations network of roads and bridges significantly
contribute to a healthy economy. In the United States, each year nearly $5 trillion
worth of goods are transported through the highway system via commercial trucks
(Bergen et al., 1998). In 2002, trucks were responsible for shipping nearly 12 billion
tons of freight representing almost 60% of all transport activities. This number is
expected to nearly double by the year 2035. The value of freight shipped by trucks
also represents a major portion of the total value of commodities shipped nationwide.
In 2002, trucks shipped about $9 trillion of freight, which is estimated to increase by
180% in the year 2035 (Freight Facts and Figures, 2007). With an increase in the
volume and value of freight shipped by trucks also comes a trend toward heavier and
larger truck combinations. Many past and recent studies also show that truck volume
and weight are increasing enormously and the change is forecasted to continue (LRFD
Bridge Design Specifications, 2004). Federal Highway Administration also indicated
that the issuance of Overweight permit continues to increase, with annual or multiple
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trip permits becoming more commonplace. The forecasted increment in freight
tonnage has also been a concern of FHWA for some time (Fu et al., 2006). From 1987
to 2002, trucks weighing between 100 kips and 130 kips increased by 238%
(Strawhorn, 2004). Figure 1.1 shows the number of overweight/oversize vehicle
permits issued nationally from 1997 through 2003. It clearly depicts a steady annual
increasing trend in the number of permits issued (Fu et al., 2006). Figure 1.2 presents
the number of divisible and non-divisible permits issued in 1985, 1990 and 1995
respectively. It shows a significant increase in the number of permit issued over the
span of a decade. The total number of permits issued increased by 60%, with divisible
load permits increasing by 148% and non-divisible by 50% from 1985 through 1995
(Truck Size and Weight Final Report). This observed growth is likely due to several
factors including economic growth, technological advances in freight transportation
logistics, and changing trade patterns resulting from the North American Free Trade
Agreement.
!Figure 1.1 Number of Overweight/Overwidth Permits Issued by States
(Fu et al., 2006)
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Figure 1.2 Overweight Permits Issued by States
(Truck Size and Weight Final Report)
With the increase in freight tonnage, highway roads and bridge safety has become
a major concern. There are 600,000 bridges in the US under a wide variety of
ownership and control. FHWA now estimates that more than 200,000 bridges are
inadequate and lists 125,000 as structurally deficient on the National Bridge Inventory
(NBI) system. There are 5,000-8,000 replacements per year so for the foreseeable
future the inventory of bridges in the US will contain numerous structures incapable of
carrying todays truck weight (Harding et al., 1990). The emphasis for highway
industries in the United States has shifted to maintenance, rehabilitation and
conservation of existing structures. Heavy truckloads not only impair the structural
load carrying capacity of the bridge but also reduce the remaining lifespan of the
bridge. Recent studies show that although overall performance of highway generally
continued to increase from 2006 to 2007, the percentage of deficient bridges has
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worsened from 24.13% to 25.29% (Hartgen et al., 2009).
The condition of highway bridges in the state of Rhode Island is even more
gruesome. The number of oversize/overweight (OS/OW) vehicle permits has seen a
steady increase in Rhode Island (Gindy et al., 2007). More and more trucks are
requesting permits to travel above the legal load limit. This coupled with an aging and
deteriorating highway bridge infrastructure as evidenced by several high profile bridge
postings (i.e. Pawtucket River Bridge and Sakonnet River Bridge), only worsens the
state of RI bridges. Rhode Island has the highest number of deficient bridges ranking
last (50
th
) in that category and 47
th
in per mile capital and bridge disbursements and
maintenance disbursements in the US (Hartgen et al., 2009). The added cost due to
overweight vehicles are in the range of $8 to $144 million for several states. On
national level, this cost amounts to $265 million to $1.11 billion (Carson, 2008). With
many old bridges rendered inadequate or structurally deficient, shortage of funds for
repair and maintenance and truck loads continually increasing, proper regulation of
overweight vehicles becomes very critical in preserving the life of the bridge and thus
keep the highway system running. In this context, the regulation of overweight
vehicles is of major concern for highway agencies.
1.1 History of Federal and State Weight Regulations
The adverse effects of heavy truck traffic on the US highway and bridge network
were highlighted as early as 1918 (Truck Size and Weight Final Report). As a result,
legislation limiting truck size and weight has been enacted for nearly a century. The
first federal regulation was introduced in 1956 through the Federal-Aid Highway Act
and limited truck weights to 73,280 lbs for gross vehicle weight, 18,000 lbs for single
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axles, and 32,000 lbs for tandem axles (Truck Size and Weight Final Report) on the
Interstate System. These limits were increased in 1975 to 80,000 lbs for gross vehicle
weight, 20,000 lbs for single axles, and 34,000 lbs for tandem axles as a result of the
Federal-Aid Highway Amendments of 1974. This legislation also required
conformance with the Federal Bridge Gross Weight Formula (Formula B), which
limits the total load on axle groupings based on the number and spacing between
axles.
Prior to federal regulations in 1956, truck size and weight limits were controlled
by individual states. As early as 1913, truck weight limits existed (i.e. Maine,
Massachusetts, Pennsylvania, Washington) and by 1933, all states had passed some
form of truck size and weight regulation (Truck Size and Weight Final Report). But
there was no Federal regulation on truck size and weight until 1956.
1.1.1 The Federal Aid Highway Act of 1956
The first Federal truck size and weight restrictions were enacted in the Federal
Aid Highway Act of 1956. It was based upon the recommendation of the-then
American Association of State Highway Officials (AASHO), subsequently renamed to
American Association of State Highway and Transportation (AASHTO). The
substantial degree of financial participation of Federal government, which was 90/10
and 80/20 Federal/State match for Interstate and State system in 1956 respectively,
warranted increased Federal involvement in setting the Interstate Truck size and
weight limits. The Federal Aid Highway Act of 1956 set the following limits on truck
size and weight:
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Maximum width limit of 96 inches; Single-axle weight limit of 18,000 lbs; Tandem-axle weight limit of 32,000 lbs; and GVW limit of 73,280 lbs.
The Federal-Aid Highway Act of 1956 was also qualified by a grandfather
clause that allowed trucks operating at loads above those set by the Federal Act given
that they are consistent with State laws in effect on July 1, 1956.
1.1.2 The Federal Aid Highway Act Amendments of 1974
The Federal Aid Highway Amendments of 1974 adopted several
recommendations from the 1964 AASHO report. The 1974 Amendments increased the
single-axle and tandem-axle weight limits to 20,000 lbs and 34,000 lbs respectively. It
also set the GVW to 80,000 lbs provided that they also meet the weight table given by
the Federal Bridge Formula B. The Federal Bridge Formula B is given by (Sivakumar
et al., 2007, Fu et al., 2006):
W = 500L
N!1+12N+ 36
"#$
%&'
eqn 1.1
where,
W=allowable gross vehicle weight of any group of two or more consecutive axles
in lbs,
L=distance between the outer axles of any group of two or more consecutive
axles in ft,
N=number of axles included in the group under consideration.
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Federal law provides exceptions to the results given by Formula B; two sets of
tandem axles can carry 34,000 lbs each if the distance between the first and last axle is
more than 36 feet apart and a single set of tandem axles spread no more than 8 feet
apart is limited to 34,000 lbs.
The exemptions of grandfather clause were further expanded to include any
State weight tables or axle spacing formulas not meeting the new bridge formula.
However, the 1974 Act did not mandate the States to adopt the new weight limits,
which led six barrier states in the Mississippi Valley to refuse the new GVW limit of
80,000 lbs. The trucking companies thus faced a barrier to cross-country interstate
commerce and the congress intervened with the Surface Transportation Assistance Act
of 1982.
1.1.3 The Surface Transportation Assistance Act (STAA) of 1982
The STAA of 1982 established the maximum and minimum standards for weight
and width and minimum standards for length on the Interstate and many Federal-aid
highways. It made the previous single-axle, tandem-axle and GVW maximum the
States could allow, the minimum they must allow on the Interstate highways,
overriding the barrier states. The STAA also made the following changes regarding
vehicle size regulations:
States were prohibited from restricting the length of trailer unit of a twin-trailerconsisting of a tractor and two trailer units, to less than 28 ft or imposing an
overall length limit.
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States were prohibited from restricting the size of a semi-trailer on a tractor-semi-trailer combination to 48 ft or imposing an overall length limit.
States were required to allow 102 inch wide vehicles on Interstate and Federal-aidhighways with 12 ft lanes.
1.1.4 The Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991
The ISTEA put a freeze on the weight and length of Long Combination Vehicles
(LCV) by only allowing LCVs that were, in actual and lawful operation under State
law on June 1, 1991. An LCV was defined as a tractor and two or more trailers and
semi-trailers operating on Interstate with GVW exceeding 80,000 lbs.
The current Federal regulations regarding the truck size and weight are as follows:
Single-axle weight limit of 20,000 lbs on the Interstate; Tandem-axle weight limit of 34,000 lbs on the Interstate; GVW limit of 80,000 lbs on the Interstate; Application of Federal Bridge Formula B for other axle groups on the Interstate; Width of 102 inches on the Interstate and Federal-aid highways; Length of 48 ft minimum for semi-trailers in a semi-trailer combination on the
Interstate and Federal-aid highways;
Length of 28 ft minimum for trailers in a twin-trailer combination on the Interstateand Federal-aid highways.
The state of Rhode Island practices the Federal size and weight limits with
modifications in order to adjust for the grandfather rights. Currently, Rhode Island
allows up to 22,400 lbs on single-axle, 36,000 lbs on tandem-axle and 80,000 lbs on
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GVW. On top of that, the modified Federal Bridge Formula is also applicable for other
axle groups. The modified Bridge Formula limits the single- and tandem-axle weight
limits to 22,400 lbs and 36,000 lbs respectively under the grandfather clause (Rhode
Island Manual for Overweight and Oversize Vehicle Permits, 1989). If the Bridge
Formula yields lower weight limits, then the grandfathered limits hold true. Table 1-1
summarizes the current Federal and State truck size and weight limits. Table 1-2
shows the development of Federal and State legislations regarding overweight
vehicles.
Table 1-1 Current Federal and State Size and Weight Regulations
OS/OW Parameter Federal Rhode Island
Single axle 20k 22.4k
Tandem axle 34k 36k
GVW 80k 80k
FBF Yes Yes (modified)
Width 8.5ft 8.5ft
Height No limit 13.5ft
Length No limit No limit
Single unit No limit 40ft
Tractor-semi-trailer No limit 48.5ft on trailer
Twin-trailers No limit 28.5ft on trailer
Table 1-2 Historical Development of Overweight Vehicles
Criteria 1956 1975 Current RI (Current)
Single Axle Wt. 18,000 20,000 20,000 22,400
Tandem Axle Wt. 32,000 34,000 34,000 36,000
GVW 73,280 80,000 80,000 80,000
FBF Inactive Enacted Holds Modified!Any vehicle violating the Federal or State size and weight regulations, as the case
may be, is required to apply and obtain a permit prior to its journey. It is very obvious
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that the permit vehicles would constitute the largest and the heaviest trucks in the
traffic. Hence, the highways and the bridges on it are more susceptible to damage from
these overweight and/or oversize vehicles than other normal traffic stream. Thus
proper regulation and management of the permit vehicles would prove to be very vital
in maintaining a safe, reliable and cost-effective road network system.
1.2 Objectives
The goal of this project is to assess the capability of the current load rating
standard permit vehicles in enveloping the effects of overweight vehicles in the State
of Rhode Island and to recommend changes if necessary (Manual for Condition
Evaluation and Load Rating of Highway Bridges Using Load and Resistance Factor
Philosophy, 2001 and Sivakumar 2009). To achieve this, the research plan will collect
representative oversize/overweight permit records from the electronic database
currently maintained by RI.gov, develop statistical descriptors for overweight permit
vehicles in Rhode Island, evaluate truck load effects (i.e. positive and negative
bending moments and shear forces) for simple and two-span continuous bridges of
varying span lengths, and identify vehicle configurations that best envelope the effects
of these overweight permit vehicles. This study will provide a realistic assessment of
the impact of overweight permit vehicles on highway bridges across the State. This
information is critically important to their continued efforts of ensuring the safety of
bridges in the State. Based on the results of this study, the Department of
Transportation may or may not elect to make adjustments to the current load rating
standard permit vehicle or their permit review process.
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This chapter has outlined the historical background of Federal and State
involvement in Size and Weight regulations of oversize/overweight permit vehicles.
Chapter two deals about the electronic database of non-divisible single trip permit
truck applications maintained by RIDOT consisting of truck information from January
2009 to December 2009. It discusses different types of permits, data quality check of
the database, size and weight characteristics of the permit database, time required for
permit reviewing and criteria for requiring a detailed RIDOT review. Size, weight and
load effects of the permit trucks reviewed by RIDMV and RIDOT were analyzed and
compared. Chapter three deals with developing a vehicle body type scheme for
overweight permit trucks in RI. Federal Highway Administration (FHWA) classes are
defined and unmodified body type schemes of New Jersey and California
Transportation are employed to define vehicle body types of RI overweight permit
vehicles. The New Jersey and California Transportation body types are then revised to
better suit the vehicle configuration of RI permit vehicles. Chapter four presents the
load effects of RI permit vehicles. The load effects caused by the permit trucks for
bridges with spans ranging from 20 ft to 200 ft are calculated in terms of maximum
positive moment, maximum 2-span continuous negative moment and maximum shear.
The load effects are then compared with those induced by standard HL-93 truck and
results are discussed. The load effects are then compared with those produced by 3-, 4-
, 5-, 6- and 8-axle standard RI permit trucks and the results are compared to check
whether the standard trucks are capable of satisfactorily enveloping the effects of the
permit trucks. New standard truck models are developed if the current ones are found
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CHAPTER 2OVERWEIGHT VEHICLE DATABASE
Any commercial vehicle exceeding the legal size and/or weight limits is required
to obtain a permit prior to its travel. Generally, oversize/overweight (OS/OW)
vehicles can be classified into two categories, namely non-divisible or non-reducible
loads and divisible or reducible loads. Divisible loads are those consisting of a
product, material or equipment that can be reduced in weight and dimension as to
comply with all statutory limits. These include ready-mix concrete, gravel, or
petroleum products. Divisible load permits are issued by the State based upon historic
grandfather rights for overweight and not oversize vehicles. These routine
permits allow unlimited intrastate travel over a years period.
Non-divisible loads, on the other hand, are those that exceed regulated weight or
dimension limits which, if separated into smaller loads or vehicles, would compromise
the intended use of the vehicle, destroy the value of the load or vehicle, or require
more than 8 work hours to dismantle using appropriate equipment. Examples of non-
divisible loads are large transformers, houses, and pieces of construction equipment.
Non-divisible load permits can be issued for loads not meeting axle, gross, or Federal
Bridge Formula requirements only when warranted by sound engineering judgment
and review of bridge structures, clearances, and road safety (Sivakumar, 2009).
In Rhode Island, three different non-divisible permits can be issued:
a. Single-trip permit issued for travel along the designated route only once withinthe five days the permit is valid. The fee for a single-trip permit is $24.50.
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b. Blanket permit issued for unlimited intrastate travel. These permits can beissued to trailers carrying boats and certain types of construction equipment that
have an overall length less than 75 and a width less than 11-11 for a 3-6 month
period (fee of $311.50) or to cranes that do not exceed 12 in width, 136 in
height, 95 in length and 130,000 lbs in GVW (Sivakumar, 2009) for period of one
year (fee of $100.00).
c. Consortium permit issued for interstate travel of non-divisible loads through anyof the five participating consortium states (Maine, Massachusetts, New
Hampshire, Rhode Island, and Vermont) along a pre-approved regional roadway
network provided the vehicles size and weight are within the specified limits
shown in Table 2-1. Operators of vehicles exceeding any of the limitations of the
envelope vehicle must obtain separate permits from each state in which travel will
occur. This agreement resulted from the 1987 New England Transportation
Consortium (NETC) Common Truck Permit Program (NETC, 1995). This
program allows a transporter to file only one application for interstate travel rather
than each individual state. The permit-issuing state is the destination state if it is
one of the five Consortium members or the entry state otherwise.
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Table 2-1 NETC Envelope Vehicle Configurations for Non-divisible Single-Trip
Permits (NETC, 1995)
Size &
Weight
Limits
Width
140Except for modular ormobile homes for which anadditional 6 overhang foreave(s) will be allowed.The greater overhang shallbe on the right-handshoulder side of thehighway.
Height 136
Length 900
AxleSpacing
Grossvehicleweight
! 5-axles! 6-axles
108,000 lbs120,000 lbs
Weight Tridem Axle 20,000 lbs/axle (60 kip total)
In Rhode Island, OS/OW vehicle permits are administered by the Rhode Island
Department of Motor Vehicles (RIDMV). This includes reviewing applications,
collecting fees, and issuing permits. RIDMV reviews all divisible load permits while
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single-trip non-divisible permits are reviewed by RIDMV and the Rhode Island
Department of Transportation (RIDOT). This Chapter presents the analysis of the
latter, with special focus on overweight non-divisible single-trip permits.
2.1 Single-Trip Oversize/Overweight Vehicle Permit Database
A database of approved non-divisible single-trip OS/OW vehicle permits was
obtained from the Rhode Island Department of Motor Vehicles (RIDMV) via the
RI.gov online permit application system (www.ri.gov/DMV/OSOW). The database
contains 9,404 records from January 2009 through December 2009 and includes
information on the applicant (i.e. company name), travel route (i.e. origin-destination,
specific route), vehicle configuration (i.e. dimensions of width, length, and height and
axle configuration including number of axles, individual axle weights and spacing, and
gross vehicle weight), and the permit review (i.e. reviewing agency, number of
submittals, and time required for review). Table 2-2 presents the details of the
database.
2.1.1 Data Quality Checks
A data quality check was performed to identify errors in the data, primarily due to
input errors by the applicant. Data quality criteria were primarily of two categories,
weight and length, and included checks on the gross vehicle weight, overall truck
length, and number of axles. Table 2-3 shows the sequence of checks used along with
the number and percent of trucks that did not meet each particular criterion.
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Table 2-2 Parameter Definition for the RI OS/OW Vehicle Permit Database
Column Field Description
1 ID 6-digit permit application identification number
2 Company Name Name of the trucking company
3 Route Specific trip route requested
4 Initials Email address of the permit reviewer
5-10Year, Month, Day,
Hour, Minute, SecondIn
Date and time permit application is submitted byapplicant
11-16Year, Month, Day,
Hour, Minute, SecondOut
Date and time permit review application iscomplete
17 Agency RI agency reviewing permit (1=DMV, 2=DOT)
18 Origin Originating state of travel (1=RI, 2=CT, 3=MA)
19 Destination Destination state of travel (1=RI, 2=CT, 3=MA)
20 SubmittalNumber of times the same permit was submittedfor review
21 Height Height of vehicle (inches)
22 GVW Gross vehicle weight (lbs)
23 Width Width of vehicle (inches)
24 Length Length of vehicle (inches)
25 NAX Number of axles
26 AXW1 Weight of axle 1 (lbs)
27 AXS1 Spacing between axles 1 and 2 (inches)28 AXW2 Weight of axle 2 (lbs)
29 AXS2 Spacing between axles 2 and 3 (inches)
... ... ...
63 AXS19 Spacing between axles 19 and 20 (inches)
64 AXW20 Weight of axle 20 (lbs)
It was found that nearly 40% of the records did not meet one of the three data
quality check criteria. The primary error identified was that the number of axle weight
entries did not match the number of axles specified by the applicant. That is, most
applicants either omitted some axle weight entries or entered an incorrect value for the
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number of axle field. This check identified 34% of the records as erroneous. An
additional 3% had individual axle weight entries that did not sum to the gross vehicle
weight specified while an additional 1% had individual axle spacing that summed to a
value greater than the overall specified truck length. In total, only 5,850 records were
used in this study. This large loss of data could have been avoided if these simple
checks were incorporated at the onset of data entry prompting the applicant to reenter
the vehicle information if any of the checks are violated.
Table 2-3 Data Quality Checks
No. CriteriaNo. of VehiclesNot Meeting
Criteria
Percent ofVehicles Not
Meeting Criteria
1Number of axle weight entries equalsthe number of axles specified
3,205 (90.2%) 34%
2GVW equals the sum of individualaxle weights
299 (8.4%) 3%
3Overall truck length greater than orequal to the sum of individual axlespacing
50 (1.4%) 1%
TOTAL 3,554 (100%) 38%
2.1.2 Vehicle Size and Weight Classification
There are four basic weight limits; single-axle, tandem-axle, gross vehicle weight,
and Federal Bridge Formula B (Formula B). In Rhode Island, the limits are 22.4 kips
for single axles, 36 kips for tandem axles, 80 kips for gross vehicle weight (GVW),
and adherence to a modified form of Formula B for all highways. The modified
Formula B is given by the same expression as the Federal Bridge Formula B in
equation 1.1 but with adjustments to allow for higher single-axle and tandem-axle
weight limits from 20 and 34 kips to 22.4 and 36 kips, respectively.
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Regarding size limits in Rhode Island, vehicles with a width greater than 8.5 ft or
a height greater than 13.5 ft are classified as oversized. There is no one overall
bumper-to-bumper length restriction but there are different restrictions depending on
the type of vehicle. The maximum length of a single unit truck is limited to 40 ft, the
length of the trailer on a tractor-semi-trailer combination is limited to 53 ft with those
greater than 486 permitted only on designated routes and the length of trailers on
twin-trailers are limited to 28.5 ft (The State of Rhode Island General Laws; Rhode
Island Manual for Overweight and Oversize Vehicle Permits, 1989). Since the dataset
used in this study did not include specifics about the body type of the vehicle, an
analysis of length could not be performed.
Table 2-4 shows the size and weight limits most often exceeded. It is important to
note that a vehicle may exceed one or more limits and therefore the total number of
limits exceeded does not sum to the total number of vehicles. With regards to vehicle
size, the analysis indicates that non-divisible single-trip permit vehicles most often
exceed the width limit (86%) while only 4% exceed the height limit.
With regard to weight, nearly half of vehicles exceeded the Formula B (53%),
GVW (47%), and tandem-axle (45%) limits while a third exceeded the single-axle
limit (33%). Upon a thorough look in to the database, it is found that a negligible
number of trucks only exceed axle limits exceeding any other weight limits. In other
words, a truck that exceeds the single- or tandem-axle limit most likely also exceeds
the GVW and/or Formula B. This is useful because it reduces the number of weight
limit checks by half and identifies the two primary limits as GVW and adherence to
Formula B. Table 2.4 also indicates that there is no significant difference between the
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stated. However, an attempt is made in this study to infer these guidelines solely from
analyzing the data in latter sections.
Figure 2.1 RI Legal Size Limits
Figure 2.2 RI Legal Weight Limits
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Table 2-5 Vehicle size and weight classification by agency
Size and Weight Characteristic Total RIDMV RIDOT
Strictly Oversize (OS) 2,778 (47.5%) 2,627 (44.9%) 151 (2.6%)
Oversize & Overweight
(OS&OW)2,611 (44.6%) 2,294 (39.2%) 317 (5.4%)
Strictly Overweight (OW) 461 (7.9%) 444 (7.6%) 17 (0.3%)
TOTAL5,850
(100%)
5,365
(91.7%)
485
(8.3%)
2.2 Characteristics of Overweight Vehicles
Overweight permit vehicles are analyzed to characterize the number of
applications approved, number of application re-submittals, origin-destination states,
number of axles, and GVW. Seasonal variations are also examined.
2.2.1 Number of Permit Applications
The characteristics of overweight vehicles are examined with the information on
3,072 valid single-trip non-divisible OW permit trucks. The database contains OW
permit vehicles with number of axles ranging from 2 to 13. There is one special 20-
axle super-load truck, with a GVW of 622,000 lbs. The permit application was
submitted in the month of August 2009 and was issued in September 2009 and it took
nearly 30 days for RIDOT to review it. The superload vehicle traveled from Rhode
Island to Connecticut. The vehicle was overheight, overwidth and overlength as well.
Since this type of truck is a one-off case, results of this truck are omitted in this study.
Vehicles with number of axles 2 and 9 or above are too few to be of any statistical
significance and hence are not considered in this study while dealing with vehicles of
specific number of axle configuration.
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Figure 2.3 shows the monthly variation of the number of overweight permit
applications approved by each agency. On average, 260 overweight permit
applications are approved each month with 230 approved by RIDMV and 30 approved
by RIDOT. It should be noted that only valid data records (i.e. those that passed the
data quality checks) were used in the analysis. The total number of approved permit
vehicles may in fact be much larger since RIDMV and RIDOT personnel would have
most likely corresponded with the motor carrier to attain valid vehicle information.
Additionally, the months of May, June and October had nearly 88% of the records
removed due to data input errors as identified by the data quality checks. Each month
only contained about 30 valid overweight applications.
Figure 2.3 Monthly Variation of Overweight Permits Approved by Each
Agency
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2.2.2 Number of Permit Re-Submittals
There are a number of reasons why a permit application is rejected but the most
common reason is that the requested route cannot accommodate the vehicle
configuration due to a width, height or a bridge capacity restriction. Whatever the
reason, the applicant often resubmits the application. Table 2-6 and Figure 2.4 show
the number of submittals for overweight vehicles by agency. It can be seen that if a
permit is approved, 94% of the time it is approved the first time it is submitted.
However, there are cases where a single application was reviewed five times before it
was approved.
Table 2-6 also shows that RIDOT had a higher rejection rate than RIDMV. That
is, 24% of applications reviewed by RIDOT required at least a second submission
versus only 4% of RIDMV reviews. This is most likely due to the complexity of the
reviews that RIDOT performs in comparison with RIDMV. RIDOT performs an
engineering analysis for each bridge along the requested route using the specific
vehicle configuration, which is more likely to result in cases where the route cannot
accommodate the load.
Since the database only contained information on approved permits, the total
number of applications reviewed by each agency is not available. However, this can
be estimated from the number of approved permits and the number of submittals. For
example, RIDMV approved 2,638 overweight permits the first time the application
was submitted, 79 applications on the second submittal, 15 applications on the third
submittal, and 6 applications on the fourth (or more) submittals. Assuming all
applications requiring at least four reviews were approved on the fourth submittal, the
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total number of overweight permits reviewed by RIDMV can be estimated to be 2,638
(85.9%) "1+79 (2.6%) "2+15 (0.5%) "3+6 (0.2%) "4=2,865.
Similarly, RIDOT is estimated to have reviewed 254 (8%)"1+60 (2%)"2+17
(0.6%) "3+3 (0.1%) "4=437 overweight permits. These numbers do not include those
applications that were rejected but never resubmitted or the applications that were
filtered out by the data quality checks. For the latter, RIDMV and RIDOT personnel
had to spend additional time figuring out the correct data entries or communicating
with the applicant.
To account for invalid records, similar re-submittal percentages were assumed for
the data filtered out by the data quality checks. That is, 52.5% (1,866) of the 3,554
records rejected are overweight, 89% (1,633) of which are reviewed by RIDMV and
11% (203) are reviewed by RIDOT. With similar percentages for the number of
submittals required, this would result in 1,551 and 29 overweight applications
reviewed by RIDMV and RIDOT respectively. This results in an estimate for the total
number of overweight applications reviewed by RIDMV and RIDOT each week as
(2,865+1551)/52=85 and (437+29)/52=9, respectively.
Table 2-6 Number of Application Submittals by Agency for Overweight Vehicles
No. of SubmittalsAgency
1 2 3 !4
Number of
OS&OW and OW
Vehicles
RIDMV2,638
(85.9%)
79
(2.6%)
15
(0.5%)
6
(0.2%)
2,738
(89%)RIDOT
254(8.3%)
60(2.0%)
17(0.6%)
3(0.1%)
334(11%)
TOTAL4,808
(94.1%)
219
(4.5%)
51
(1.0%)
13
(0.3%)
3,072
(100%)
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Figure 2.4 Number of Submittals for Each Agency
2.2.3 Time Required to Review Permits
The time required to review overweight vehicles is of interest, particularly for
RIDOT engineers, because it is an indication of their added responsibilities as well as
of the efficiency of the permit review process. The dataset includes fields for the date
and time, to the second, of when the application was submitted and the review was
completed. Figure 2.5 shows the number of days it took each agency to review
overweight permit applications. Generally, it takes RIDMV less than one day to
review 96% of its permit applications and five days to review all applications. The
latter is most likely due to a situation where a permit is submitted on a Friday and
accepted on Tuesday after a 3-day holiday weekend. RIDOT, on the other hand,
reviews about 60% of the applications in less than one day and generally requires
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about 6 days to review 96% and two weeks to review all overweight permits. This is
reasonable given the laborious nature of the engineering review process and that no
full-time engineer is dedicated to permit review.
Figure 2.5 Time Required to Review Overweight Permits by Agency
Table 2-7 shows the number of days it took to review each permit by the number
of submittals. It was expected that an application that had been submitted several
times (i.e. have a high number of submittals) would be familiar to the reviewer and
would therefore require less time to review. However, as shown in Figure 2.6, there
was no real savings of time in reviewing the same permit more than twice, particularly
for RIDOT. The average time required for reviewing was found to actually increase
with the number of submittals for both agencies.
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Table 2-8 shows the statistical parameters for the time required to review
overweight permits by agency. On average, it takes RIDMV about 4 hours to review
first submittals compared with 30 hours for RIDOT.
Table 2-7 Time Required to Review Overweight Permits by Agency and Number
of Submittals
Number of overweight permits reviewed
RIDMV RIDOT
No. of Submittals No. of SubmittalsDays
1 2 3 !4 Total 1 2 3 !4 Total
1 2581 67 13 2 2663 181 12 3 0 196
2 3 2 1 1 7 24 18 3 0 45
3 49 2 1 2 54 11 11 2 0 24
4 5 6 0 0 11 19 10 5 0 34
5 0 2 0 1 3 6 4 1 1 12
6 0 0 0 0 0 5 0 0 0 5
7 0 0 0 0 0 6 2 2 1 11
!8 0 0 0 0 0 2 3 1 1 7
Total 2638 79 15 6 2738 254 60 17 3 334
Table 2-8 Statistical Parameters for the Time Required to Review Overweight
Permits by Agency
RIDMV RIDOT
No. of Submittals No. of Submittals
Statistical
Parameters
(hours 1 2 3 !4 1 2 3 !4
Mean () 4 20 17 44 29 57 78 158
Std. Dev (!) 10 28 18 40 38 55 59 66
CoV (%) 295 145 102 91 132 96 75 42
Minimum 0.0 0.4 0.5 1 0.1 3 2 92
Maximum 92 115 71 98 265 334 215 264
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Figure 2.6 Statistical Variation of the Time Required to Review Overweight
Permits with the Number of Permit Re-submittals
2.2.4 Requested Travel Route
The requested origin-destination states for overweight vehicles are presented in
Figure 2.7. For interstate travel, no distinction is made between the origin or
destination state. That is, travel from CT to RI is grouped with travel from RI to CT.
Results indicate that 93% of non-divisible single-trip permits were requested for
interstate travel while only 7% was for intrastate travel (RI-RI). Furthermore, 10% of
overweight vehicles used RI as a throughway to neighboring states (CT-MA) while
83% of vehicles originated or ended in RI.
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Figure 2.7 Requested Origin-Destination States for Overweight Permit Vehicles
2.2.5 Number of Axles
The number of axles of overweight permit vehicles ranged from 2 to 13 axles with
very few 2-axle and 9- or more axles. There was one permit approved for the travel of
a 20-axle, 622-kip superload from RI to CT that took nearly 30 days to review. Since
this type of truck is a special case, it was omitted from the analysis.
Figure 2.8 presents the distribution of the number of axles of the overweight
permit vehicles. Results indicate that nearly half of the population is 5-axle trucks
(53%) followed by 6- (24%), 7- (9%), 4- (8%) and 8-axle (3%) vehicles respectively.
This result is also seen in Chapter 3 where vehicle body type is examined. It is found
that the most common truck body type is that of a FHWA Class 9, 5-axle tractor-
trailer followed by a Class 10, 6-axle truck.
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Figure 2.8 Variation of Number of Axles for Overweight Vehicles
2.2.6 Gross Vehicle Weight
The Cumulative Distribution Frequency (CDF) of the GVW is plotted in Figure
2.9 on normal probability paper (NPP) for 3 to 8-axle overweight vehicles. In this, the
vertical axis represents the inverse of the standard normal distribution function and is
given by z =!"1[F(x)] , where F(x) is the cumulative distribution of random variable,
X (i.e. gross vehicle weight). Thus, the value of x corresponding to z = 0
corresponds to the mean value of X , while values corresponding to z = 1, z = 2 and
z = 3 represent the 84th, 98th, and 99.8th percentile respectively. The statistical
parameters are summarized in Table 2-9.
In general, average and maximum GVW increase with an increasing number of
axles as expected. The average GVW for 3-, 4-, 5-, 6-, 7-, and 8-axles are found to be
69, 71, 94, 106, 124, and 139 kips, respectively with a 20% Coefficient of Variance
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(CoV). The maximum vehicles weights were 93, 130, 132, 146, 155 and 172 kips,
respectively. It is interesting to note that there was only a 2-kip difference between
the maximum GVW on a 4-axle truck when compared with a 5-axle truck. This can
have serious implications on highway bridges if more 4-axle vehicles are loaded to
such levels since they often have a short wheelbase and tend to concentrate the axle
loads.
Figure 2.9 CDF of GVW of Overweight Vehicles by Number of Axles
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Figure 2.10 Seasonal Variation of GVW
Table 2-9 Statistical Parameters of GVW for Different Number of Axles
Description 3-axle 4-axle 5-axle 6-axle 7-axle 8-axle
Mean () 69 71 94 106 124 139
Std. Dev. (!) 14 20 17 19 22 24CoV 20% 27% 18% 18% 18% 18%
Minimum 45 41 40 49 55 60
Maximum 93 130 132 146 155 172
Figure 2.10 shows the variation of the GVW over the entire year of 2009. The
monthly variation of the mean, maximum and 95% percentile, denoted by W95, are
presented. No real trend can be identified with regards to gross vehicle weight.
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2.3 Criteria for Requiring a RIDOT Review
As mentioned earlier, the criteria used by the RIDMV for requiring a RIDOT
engineering review for non-divisible single-trip permits are not explicitly known. In
this study an attempt is made to infer these criteria solely based on the size and weight
characteristics of the permit vehicles reviewed by each agency.
2.3.1 Size Characteristics
Three size parameters are considered, namely the number of axles, vehicle width,
and vehicle height.
Figure 2.11 Variation of Number of Axles for All Permit Vehicles
As far as the number of axles is concerned, almost all of the permit vehicles with 6- or
less axles are found to be reviewed by RIDMV (97%) as shown in Figure 2.11. For
permit vehicles with 7- or more axles, although RIDOT reviewed most of the permit
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vehicles (68%), RIDMV was still found to review a significant portion of permit
vehicles with 7- or more axles. Therefore, there is no apparent criterion found with
respect to number of axles.
With regards to vehicle width and height, only strictly oversize vehicles (OS)
were examined. This was necessary to isolate the threshold used by the RIDMV. This
data subset included 2,778 vehicles (95% reviewed by RIDMV and 5% reviewed by
RIDOT) of which 2,339 exceeded both the legal width and height limits, 114 only
exceeded the legal width limit (overwidth), and 19 only exceeded the height limit
(overheight). This accounted for about 89% of the OS data subset. The remaining
11% of OS vehicles most likely exceed the legal length limit. Table 2-10 presents the
breakdown of these numbers by agency.
Table 2-10 Strictly Oversize Vehicles
Strictly Oversize RIDMV RIDOT Total
Strictly Overwidth 2,313(83%)
26(1%)
2,339(84%)
Overwidth and Overheight 10(0.4%)
104(4%)
114(4%)
Strictly Overheight 2(0.1%)
17(1%)
19(1%)
Sub-Total 2,325(84%)
147
(5%)
2,472
(89%)
Total 2,627(95%)
151
(5%)
2,778
(100%)
Figures 2.12 and 2.13 present the CDF plots for the width and height of strictly
oversize (OS) vehicles, respectively, by agency along with the legal limits. Regarding
width, both RIDMV and RIDOT reviewed vehicles of widths ranging from the 102
limit (8-6) to 192 (16) while only RIDOT reviewed vehicles having widths greater
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than 192 (16). If only the overwidth vehicles are considered, as shown in Figure
2.14, similar trends to those of strictly oversize vehicles were found.
With regard to vehicle height, nearly all overheight vehicles were reviewed by
RIDOT with only 2 out of the 19 vehicles reviewed by RIDMV. From conversations
with RIDOT Bridge engineers, these incidents were probably errors on the part of the
RIDMV personnel, which were later manually forwarded to RIDOT engineers for
review, which was not reflected in the dataset. Figure 2.13 shows the CDF of the
vehicle height for strictly oversize vehicles. A clear cut-off point is evident at the
legal height limit that separates both agencies.
Figure 2.12 Width of Strictly OW Vehicles
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Figure 2.13 Height of Strictly OS Vehicles
Figure 2.14 Width of Strictly Overwidth Vehicles
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2.3.2 Weight Characteristics
A similar approach is taken to identify weight-related guidelines for warranting a
RIDOT review. In general, RIDMV personnel can base their decision for requiring a
RIDOT review on three vehicle weights directly available to them, namely single-axle,
tandem-axle, and GVW. However, since it was found that most vehicles that
exceeded an axle limit also exceeded a GVW and/or a Formula B limit, only GVW is
considered herein.
Figure 2.15 presents the CDF of the GVW for strictly overweight (OW) vehicles
for each agency. It can be seen that, in general, RIDMV reviews permits for loads up
to 130 kips while anything greater is solely reviewed by RIDOT. There was only one
case where an 80-kip load was reviewed by RIDOT, which could have been forwarded
in error. It is interesting to note that the RIDMV solely reviews all blanket permits for
cranes up to 130 kips. This may explain part of their rational for internally handling
single-trip non-divisible loads up to 130 kips as well.!
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Figure 2.15 GVW of Strictly OW Vehicles
2.4 Load Effects of Overweight Vehicles
Although the total load is an important factor in bridge analysis, the individual
axle weights and the distribution of axles along the vehicle wheelbase are also
critically important. This is particularly true for short-span bridges where the vehicle
wheelbase may exceed the total length of the bridge. In such cases, not all axle groups
are simultaneously on the bridge and the individual axle groups become more
important than the total load. One way of accounting for the widely varying axle
configurations of each permit vehicle, is to use the load effect (i.e. bending moment or
shear force) imposed on the bridge by each vehicle.
For each of the 5,850 permit vehicles, positive and negative bending moments
"#and "$ and shear forces % are calculated for a wide range of span lengths ranging
from 20 ft to 200 ft at 20-ft intervals. Both simply-supported and continuous bridges
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Figure 2.16 Positive Moment for Short, Medium and Long Span by Agency
Figure 2.17 Negative Moment for Short, Medium and Long Span by Agency
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Figure 2.18 Shear for Short, Medium and Long Span by Agency
Table 2-11 Approximate Normal Statistical Parameters of Positive Moment
20 ft 120 ft 200 ftM+
TRUCK/ M+
HL-93
Statistical
Parameter DMV DOT DMV DOT DMV DOTMean () 0.85 0.92 0.69 0.80 0.65 0.77
Std. Dev. (!) 0.13 0.15 0.10 0.16 0.09 0.17
CoV 15% 16% 15% 20% 14% 22%
Minimum 0.39 0.29 0.29 0.28 0.30 0.27
Maximum 1.61 1.29 1.46 1.21 1.37 1.18
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Table 2-12 Approximate Normal Statistical Parameters of Negative Moment
20 ft 120 ft 200 ftM+
TRUCK/ M+
HL-93
Statistical
ParameterDMV DOT DMV DOT DMV DOT
Mean () 0.81 0.88 0.43 0.52 0.39 0.47Std. Dev. (!) 0.17 0.16 0.06 0.12 0.06 0.11
CoV 21% 19% 14% 23% 15% 23%
Minimum 0.35 0.17 0.32 0.16 0.20 0.15
Maximum 1.65 0.97 1.61 0.91 1.17 0.86
Table 2-13 Approximate Normal Statistical Parameters of Shear
20 ft 120 ft 200 ftM+
TRUCK/ M+
HL-93
StatisticalParameter
DMV DOT DMV DOT DMV DOT
Mean () 0.88 0.93 0.79 0.93 0.70 0.83
Std. Dev. (!) 0.14 0.15 0.11 0.19 0.10 0.18
CoV 16% 16% 14% 21% 15% 22%
Minimum 0.34 0.32 0.34 0.30 0.32 0.29
Maximum 1.5 1.33 1.12 1.22 1.021 1.22
Figure 2.19 presents the percent of load effects above a ratio of 1.0 for different
bridge spans by agency. The load effects induced by trucks reviewed by RIDMV are
shown by solid lines whereas those by RIDOT are shown by dashed lines. Positive
bending moment, negative bending moment and shear are represented by square,
circle and triangle symbols respectively. Table 2-14 summarizes the probability of
exceedances of load effects for various spans shown in Figure 2.19. Again, in general
the probability of exceedances of trucks reviewed by RIDOT is greater than those of
RIDMV reviewed trucks. The margin by which the former is higher than latter ranges
from -0.3% (i.e., probability of exceedance of RIDMV reviewed trucks is greater than
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that of RIDOT) to 34.3%. For spans less than 80 feet, the probability of exceedance of
RIDMV and RIDOT reviewed trucks are found to be quite similar.
Thus it can be inferred that there is a strong possibility that RIDMV is reviewing
permit applications of trucks, which induce load effects greater than those being
reviewed by RIDOT. Conversely, RIDOT is also getting permit applications of trucks
forwarded from RIDMV with load effects which are seemingly less than those being
reviewed by RIDMV. However it must also be noted that the vehicles with smaller
load effects might have been forwarded to RIDOT to check for its size restrictions
rather than its weight restrictions, as it is not clear from the database itself as to the
reason for any permit being forwarded to RIDOT from RIDMV. This could be very
crucial since it has been already mentioned that most of the trucks in the database are
found to violate both the size and weight restrictions. Under any circumstances, it
should also be noted that there is clearly a need to delineate a criteria that separates
permit applications reviewed by RIDMV and RIDOT.
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Figure 2.19 Probability of Exceedance of Load Effects by Agency
Table 2-14 Table of Probability of Exceedance of HL93 Load Effects
Positive Moment, % Negative Moment, % Shear, %Span
RIDMV RIDOT RIDMV RIDOT RIDMV RIDOT
20 ft 7.6 31.8 6.2 5.1 8.7 45.340 ft 7.2 49.1 74.8 77.0 5.1 9.4
60 ft 3.4 3.6 - 21.0 5.0 9.2
80 ft 2.3 1.5 - - 3.7 30.9
100 ft 1.9 1.7 - - 3.0 38.5
120 ft 1.5 2.3 - - 1.8 33.8
140 ft 0.9 2.4 - - 1.0 30.1
160 ft 0.6 2.6 - - 0.7 25.1
180 ft - 2.3 - - 0.1 15.4
200 ft - 1.6 - - 0.1 6.1
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Figure 2.20 Average and Maximum Load Effects for All Spans by Agency
Figure 2.20 shows a plot of average and maximum normalized "#&!"$, and % for
all spans by agency. Solid symbols with solid represent RIDMV while hollow
symbols with dashed lines represent RIDOT. Again, it can be seen that although the
average load effects of RIDOT approved vehicles are higher than those of RIDMV
approved vehicles, the range is almost the same and for shorter spans, the maximum
load effects of RIDMV approved vehicles are higher than RIDOT approved ones.
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CHAPTER 3VEHICLE BODY TYPES
The Federal Highway Administration (FHWA) classifies vehicles using a 13-
category scheme depending on the use (i.e. passenger or commodity), number of axles
and number of power and trailer units as shown in Table 3-1. This algorithm, referred
to as Scheme F, was developed in the mid-1980s by the Maine DOT (Wyman et al.,
1985). All states currently use this classification scheme or some variation of it for
classifying vehicles (Traffic Monitoring Guide 2001). Rhode Island uses an
unmodified version of the scheme to classify its vehicles. From Table 3-1, it is seen
that nine classes are reserved for trucks, namely Classes 5-7 for single-unit trucks,
Classes 8-10 for single trailer trucks, and Classes 11-13 for multi-trailer trucks.
Within each FHWA class, however, vehicles can take on several different body
types. A vehicle body type describes a more specific grouping of axles within a
particular vehicle class. For example, all 5-axle semi-tractor trailers are classified as
Class 9 vehicles although they can take on different axle configurations such as a
single-tandem-tandem or a single-tandem-spread tandem or any other axle
arrangement. If a more detailed analysis of vehicle characteristics is of interest, then
identifying the different vehicle body types is necessary.
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Table 3-1 FHWA Vehicle Classification (Traffic Monitoring Guide, 2001)
Class Vehicle Description Schematic
0Unclassified vehicles which do not fit into any other
classification
1Motorcycles. All two-or three wheeled motorizedvehicles. This category includes motorcycles, motorscooters, mopeds, and all three-wheel motorcycles.
2Passenger Cars. All sedans, coupes, and station wagonsmanufactured primarily for purpose of carryingpassengers.
3Other two-axle, four-tire single units. Included in thisclassification are pickups, vans, campers, ambulances.
4
Buses. All vehicles manufactured as traditional passenger-
carrying buses with two axles and six tires or three ormore axles.
5Two-Axle Single Unit Trucks. All vehicles on a singleframe including trucks, camping and recreation vehicles.
6Three-Axle Single Unit Trucks. All vehicles on a singleframe including trucks, camping and recreational vehicles.
7Four- or more Axle Single Unit Trucks. All vehicles ona single frame with four- or more axles.
8
Four- or Less Axle Single Trailer Trucks. All vehicleswith four or less axles consisting of two units, one ofwhich is tractor or straight truck power unit.
9Five-Axle Single Trailer Trucks. All five-axle vehiclesconsisting of two units, one of which is a tractor orstraight truck power unit.
10Six-or More Axle Single Trailer Trucks. All vehicleswith six- or more axles consisting of two units, one ofwhich is a tractor or straight truck power unit.
11Five-or Less Axle Multi-Trailer Trucks. All vehicleswith five or less axles consisting of three or more units,one of which is a tractor or straight truck power unit.
12Six-Axle Multi-Trailer Trucks. All six-axle vehiclesconsisting of three or more units, one of which is a tractoror straight truck power unit.
13Seven- or More Axle Multi-Trailer Trucks. All vehicleswith seven- or more axles consisting of three or moreunits, one of which is a tractor unit.
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3.1 Vehicle Body Types
Two different vehicle body type schemes are examined, namely that used by
International Road Dynamics (IRD) for the State of New Jersey (International Road
Dynamics Inc, 1999) and that used by the California Department of Transportation,
Caltrans, (Lu et al., 2002). Both body type schemes are based on the FHWA Scheme
F classification with some minor modifications.
Table 3-2 presents the NJ vehicle body types for trucks (i.e. vehicle class 5 and
above) of 3-8 axles. In general, since these schemes are used for normal truck traffic,
which contains very few vehicles with large number of axles, the axle configurations
for vehicles with 9 or more axles are very general and can be considered as catch-all
types and are therefore not used in this study. Similarly, Table 3-3 presents the
Caltrans vehicle body type scheme for trucks of 3-6 axles. In total, 20 and 10 body
types can be uniquely identified for the NJ and Caltrans schemes respectively.
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Table 3-2 New Jersey Vehicle Body Type (International Road Dynamics Inc, 1999)
Axle Spacing, ft GVWNo. of
Axles
FHWA
Class
Body
Types 1-2 2-3 3-4 4-5 5-6 6-7 7-8 Min Max
6 NJ10 0-20 0-5.8 0 100
6 NJ11 25.5-40 0-5.8 0 1503
8 NJ12 0-20 5.8-40 0 150
7 NJ17 0-40 0-9.8 0-5.8 0 150
7 NJ18 0-5.8 0-40 0-5.8 0 150
8 NJ19 0-40 0-40 0-5.8 0 1504
8 NJ20 0-40 0-5.8 0-40 0 221
7 NJ21 0-40 0-5.8 0-5.8 0-5.8 0 221
9 NJ22 0-40 0-5.8 0-40 0-5.8 0 221
9 NJ23 0-40 0-5.8 0-40 0-11.7 0 221
11 NJ24 0-14.2 0-40 0-40 0-40 0 221
5
9 NJ25 0-40 0-40 0-40 0-40 0 221
7 NJ26 0-40 0-5.8 0-5.8 0-5.8 0-5.8 0 221
10 NJ27 0-40 0-5.8 0-40 0-40 0-5.8 0 221
10 NJ28 0-40 0-40 0-5.8 0-5.8 0-5.8 0 2216
12 NJ29 0-40 0-40 0-40 0-40 0-40 0 221
10 NJ30 8.2-20 3.3-8.2 3.3-8.2 3.3-8.2 3.3-8.2 3.3-8.2 0 2217
13 NJ31 0-40 0-40 0-40 0-40 0-40 0-40 0 221
10 NJ32 8.2-20 0-8.2 0-8.2 8.2-40 0-8.2 0-8.2 0-8.2 0 2218
13 NJ33 0-40 0-40 0-40 0-40 0-40 0-40 0-40 0 221
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Table 3-3 Caltrans Vehicle Body Type (Lu et al., 2002)
Axle Spacing, ft GVW, kipsNo. of
Axles
FHWA
Class
Body
Types 1-2 2-3 3-4 4-5 5-6 Min Max
6 CAL10 6-23.09 6-25 - - - 12 -
3 8 CAL11 6-23 6-25 - - - 20 -
7 CAL15 6-23.09 11-40 3-12.99 - - 12 -
8 CAL16 6-23 6-25 13-44 - - 12 -4
8 CAL17 6-23 3-5.99 3-11.99 - - 20 -
9 CAL19 6-26 3-5.99 6-46 3-10.99 - 12 -
11 CAL20 6-26 11-26 6-20 11-26 - 12 -5
14 CAL21 6-26 3-5.99 6-23 11-27 - 12 -
10 CAL22 6-26 3-5.99 6-46 3-11.99 3-10.99 12 -6
12 CAL23 6-26 3-5.99 11-26 6-24 11-26 12 -
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Since the OS/OW non-divisible single-trip permit vehicle database used in this
study did not include vehicle class, only the number of axles, GVW and individual
axle spacing were used to identify the vehicle body type. Figures 3.1 and 3.2 present
the distributions of the RI overweight permit vehicles based on the NJ and Caltrans
schemes, respectively. It can be seen that more than 33% of the vehicles were
unclassified using either scheme. As a result, some minor modifications were made to
each scheme as follows:
1. All tandem axle spacing were widened up to 8 ft per definition by the FederalBridge Formula B
2. AXS3 for NJ25, NJ27, and NJ29 was widened from 0-40 ft to 0-50 ft3. AXS3 for CA21, CA22, and CA23 was widened from 0-40 ft to 0-50 ft4. AXS4 for catch-all NJ31 and NJ33 was widened from 0-40 ft to 0-70 ft5. CA21A was introduced as a new 5-axle catch-all body type.
In addition, following a close examination of the unclassified vehicles, the
following two changes were made. These two modifications do not necessarily reduce
the number of unclassified vehicles but improved the vehicle body type classification
because they narrowed a wide axle spacing range and more specifically identified a
body type.
6. AXS4 for NJ25 was reduced from 0-40 ft to 0-11 ft7. AXS4 for NJ27 was reduced from 0-40 ft to 0-12.6 ft
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The original and revised axle spacing for both schemes are presented in Table
3-4 with modifications shown in bold print. Additionally, similar NJ and CA vehicle
body types are now presented alongside one another. For example, NJ22, NJ23 and
CA19 all describe typical 5-axle tractor-trailer trucks and hence are presented along a
single row.
The body type distributions of the RI overweight vehicle permits using the
revised schemes are shown in Figures 3.1 and 3.2 and are labeled as Rev-NJ and Rev-
CA. The number of unclassified vehicles has now been reduced to 4% and 10% for the
NJ and CA schemes, respectively.
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Figure 3.1 Original and Revised New Jersey Body Types
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Figure 3.2 Original and Revised Caltrans Body Types
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Table 3-4 Original and Revised Body Types
Axle Spacing, ft Axle Spacing, ftNo. of
Axles
FHWA
Class
NJ Body
Types Original Revised
CA
Body
TypesOriginal Revised
NJ10 0-20;0-5.8 0-20;0-86
NJ1125.5-40; 0-
5.825.5-40;0-8
CA106-23.09;3-
5.99
6-23.09;3-
83
8 NJ12 0-20; 5.8-40 0-20;8-40 CA116.0-
23.0;11-40
6-23;11-
40
7 NJ170-40;0-9.8;0-
5.8
0-40;0-
9.8;0-8CA15
6-23.09;3-
5.99;3-
12.99
6-23.09;3-
8;3-12.99
NJ200-40;0-5.8;0-
40
0-40;0-8;0-
40CA16
6-23;3-
5.99;13-44
6-23;3-
8;13-44
8
NJ19 0-40;0-40;0-5.8
0-40;0-40;0-8
CA17 6-23;11-44;3-11.99
6-23; 11-
44; 3-
11.99
4
7 NJ180-5.8;0-40;0-
5.8
0-8;0-40;0-
8
7 NJ210-40;0-5.8;0-
5.8;0-5.8
0-40;0-8;0-
8;0-8
NJ220-40;0-5.8;0-
40;0-5.8
0-40;0-8;0-
40;0-89
NJ230-40;0-5.8;0-
40;0-11.7
0-40;0-8;0-
40;0-11.7
CA19
6-26;3-
5.99;6-
46;3-10.99
6-26;3-
8;6-46;3-
10.99
11 NJ240-14.2; 0-
40;0-40;0-40
0-14.2;0-40;0-40;0-
40
CA206-26;11-
26;6-
20;11-26
6-26;11-26;6-
20;11-26
9 NJ250-40;0-40;0-
40;0-40
0-40;0-
40;0-50;0-
11
14 CA21
6-26;3-
5.99;6-
23;11-27
5
9 CA21A
0-40;0-
40;0-40;0-
40
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Table 3-4 Original and Revised Body Types
Axle Spacing, ft Axle Spacing, ftNo. of
Axles
FHWA
Class
NJ Body
Types Original Revised
CA
Body
TypesOriginal Revised
7 NJ260-40;0-5.8;0-5.8;0-5.8;0-
5.8
0-40;0-8;0-8;0-8;0-8
- - -
10 NJ270-40;0-5.8;0-
40;0-40;0-5.8
0-40;0-8;0-
50;0-12.6;0-8 CA22
6-26;3-
5.99;6-46;3-
11.99;3-10.99
6-26;3-
8;0-50;3-11.99;3-
10.99
10 NJ28
0-40;0-40;0-
5.8;0-5.8;0-5.8
0-40;0-
40;0-8;0-8;0-8
- - -
6
12 NJ290-40;0-40;0-40;0-40;0-40
0-40;0-40;0-50;0-
40;0-40
CA23
6-26;3-5.99;11-
26;6-24;11-26
6-26;3-8;11-50;6-
24;11-26
10 NJ30
8.2-20; 3.3-
8.2; 3.3-8.2;3.3-8.2; 3.3-
8.2; 3.3-8.2
8.2-20; 3.3-
8.2; 3.3-8.2; 3.3-
8.2; 3.3-8.2; 3.3-8.27
13 NJ31
0-40;0-40;0-
40;0-40;0-40;0-40
0-40;0-40;0-40;0-
70;0-40;0-40
10 NJ32
8.2-20; 0-
8.2;0-8.2;8-40;0-8.2;0-
8.2;0-8.2
8.2-20;0-
8.2;0-8.2;8-40;0-8.2;0-
8.2;0-8.28
13 NJ330-40;0-40;0-
40;0-40;0-40;0-40;0-40
0-40;0-
40;0-40;0-70;0-40;0-
40;0-40
Table 3.5 presents the most frequent vehicle body types found in Rhode Island
along with their number of axles, FHWA class and their axle configuration. It can be
seen that the most frequent trucks are 5- and 6-axle single-trailer trucks with axle
Contd..
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configurations of single-tandem-tandem and single-tandem-spread tandem,
respectively, accounting for about 50% of the truck population.
Table 3-5 Most Frequent Body Types
NJ CANo. of
Axles
FHWA
Class Body
TypesNumber
Body
TypesNumber
Axle
Configuration1(NJ/CA)
4 8 NJ1993
(3.03%)CA17
64(2.08%)
S-S-D/S-S-SD
NJ 22745
(24.25%)CA19
836
(27.21%)S-D-D&SD/S-D-SD
5 9
NJ 2349
(1.59%)- - -
6 10 NJ 27
700
(22.79%) CA22
689
(22.43%) S-D-ST/S-D-ST
8 13 NJ3279
(2.57%)- - S-T-Q
Total -1,666
(54.23%)-
1,589
(51.73%)-
Figure 3.3 shows the distribution of vehicle class of the RI overweight dataset
based on the revised NJ and CA body types for classes 6 and above. It is clear that
Class 9 (i.e. 5-axle single trailer trucks) and Class 10 vehicles (i.e. 6- or more axle
single trailer trucks) are the most common overweight trucks in RI. Class 9 and Class
10 trucks are comprised of 49.7% and 25.9% of the single-trip overweight permit
truck population respectively.
1S single, D tandem, SD spread tandem, T tridem, ST spread tridem, Q - quadrem
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Figure 3.3 FHWA Classification
3.2 Comparison of RI Body Types with Previous Studies
Prezioso, A. (2008) also defined RI vehicle body types for OS/OW permit
vehicles. The study was based on 294 non-divisible OS