05_5_torbic_recommendedchangesinfuturedesignvehicles
TRANSCRIPT
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
1/30
Recommended Changes in Future
Design Vehicles for Purposes ofGeometric Design of U.S. Highways
and Streets
Authors:
Darren J. TorbicDouglas W. Harwood
June 21, 2006
9th International Symposium on Heavy Vehicle
Weights and Dimensions
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
2/30
Objectives
NCHRP Report 505: Review of TruckCharacteristics as Factors in Roadway Design
Ensure that geometric design criteria for trucks can
reasonably accommodate the dimensions of current and
future trucks using the U.S. highway system Recommend appropriate modifications and/or additions to
the AASHTO Green Book
Focus on Design Vehicle Fleet
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
3/30
Outline
Overview of design vehicles Future changes to the U.S. truck fleet
Single-unit trucks
Single-trailer combinations Double-trailer combinations
Triple-trailer combinations
Summary of design vehicle recommendations
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
4/30
Overview of Design Vehicles
Physical characteristics and proportions of vehiclesrepresent key controls in highway geometricdesign
2004 AASHTO Green Book presents design
vehicle dimensions and characteristics for 19design vehicles 8 trucks
Design vehicles:
Represent categories of vehicles Do not represent typical vehicles, but largest vehicles in
class
Selected or chosen by designer
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
5/30
Future Changes to U.S. Truck Fleet
Charged with assessing effect on geometric design of bothcurrent and future truck populations
Current truck fleet assessed using 1997 Vehicle Inventory
and Use Survey (VIUS) and field data
Future truck population hypothesized based upon: Current truck population
Trends in current truck population
Likelihood of changes in size and weight laws and regulations
Economics of trucking industry
TRB Special Report 267 - Regulation of Weights, Lengths, and
Widths of Commercial Motor Vehicles (2002)
North American Free Trade Agreement (NAFTA)
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
6/30
Recommendations
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
7/30
Single-Unit Trucks
Current SU design vehicle
2 axles
Overall length 9.15 m (30 ft) Wheelbase 6.10 m (20 ft)
Recommend retaining current SU design vehicle and adding
a second larger SU design vehicle
Based on numbers and VMT
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
8/30
Single-Unit Trucks (cont)
New recommended SU design vehicle [SU-8 (SU-25)]
3 axles
Overall length 12.04 m (39.5 ft)
Wheelbase 7.62 m (25 ft)
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
9/30
Single-Trailer Combinations
Green Book includes 4 classes of single-trailer
combination design vehicles: WB-12 (WB-40) [10.1 m (33 ft) trailer]
WB-15 (WB-50) [13.0 m (42.5 ft) trailer]
WB-19 (WB-62) [14.6 m (48 ft) trailer]
WB-20 (WB-65 or WB-67) [16.2 m (53 ft) trailer]
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
10/30
Single-Trailer: WB-12 (WB-40)
Rarely seen today on highways
May be appropriate for design of local roads and streets
Appropriate as container-carrying vehicle Retain as design vehicle but indicate:
Appropriate for local streets not used by larger combinationvehicles and for access roads to ports and train yards wherecontainer traffic might predominate
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
11/30
Single-Trailer: WB-15 (WB-50)
Rarely seen today on highways
Prior to 1982 Surface Transportation Assistance Act (STAA), trailersize quite common
STAA mandated use of 14.6 m (48 ft) trailers on NN
Today 12.2 13.7 m (40 45 ft) trailers have largely disappeared 8 % of single-trailer combinations
Very limited use as design vehicle
Recommend eliminating as design vehicle in Green Book
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
12/30
Single-Trailer: WB-19 (WB-62)
Nearly largest tractor-semitrailer combination on highway at one time WB-20 (WB-65 or WB-67) with 16.2 m (53 ft) trailer perhaps more common today
Retain because it represents:
Vehicle size limit specified by law Very closely the offtracking performance of longer trucks with rear axles pulled forward to
meet kingpin to center of rear tandem (KCRT) distance requirements
Slightly modify KCRT Current KCRT distance on WB-19 (WB-62) is 12.3 m (40.5 ft)
KCRT distance of 12.5 m (41 ft) more common (19 states)
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
13/30
Single-Trailer: WB-20 (WB-65)
Can operate in most states on NN and state routes
VIUS data indicate 22.4 % of VMT by trucks are single-trailers
with 16.2 m (53 ft) trailers or more
Trucks with 16.2 m (53 ft) trailers constitute 47 % of all
combination trucks
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
14/30
Single-Trailer: WB-20 (WB-67)
Identical to WB-20 (WB-65) except rear tandem is positioned closer to rear of trailer KCRT of WB-20 (WB-65) is 13.26 m (43.5 ft)
KCRT of WB-20 (WB-67) is 13.87 m (45.5 ft)
No good reason to include both vehicles in Green Book Recommend including only WB-20 (WB-67):
Has greater turning radius, offtracking, and swept path width
If designer is considering the offtracking and swept path of a single-trailercombination with a 16.2 m (53 ft) trailer and 12.5 m (41 ft) KCRT WB-19 (WB-62) should be used
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
15/30
Single-Trailer: WB-22 (WB-71)
8 states permit trucks with trailer lengths > 16.2 m (53 ft) to
operate on NN
Not recommended for inclusion as design vehicle at present time Appropriate design vehicle developed for future consideration
should numbers and proportions increase
Designated WB-22 (WB-71)
Represents incremental increase in size to WB-20 (WB-67)
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
16/30
Single-Trailer: 6 Axle Combination
Future legislation may allow states to issue permits
for 6 axle (i.e., single steering, tandem drive, andtridem rear axles) tractor-semitrailers withmaximum weights up to 35,400 kg (90,000 lb) Recommendation provided in TRB Special Report 267
6 axle tractor-semitrailers allowed to operate now No advantage over 5 axle combinations with current GVW
and axle limits
6 axle tractor-semitrailers would impact pavement
and bridge design, but would not impact geometricdesign Not recommended for inclusion in Green Book
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
17/30
Double-Trailer Combinations
Green Book includes 2 classes of double-trailer
combination design vehicles: WB-20D (WB-67D) with twin 8.7 m (28.5 ft) trailers
WB-33 (WB-109D) with two 14.6 m (48 ft) trailers
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
18/30
Double-Trailer: WB-20D (WB-67D)
Permitted to operate on NN since 1982
Common on intercity roads
Circumstances where WB-20D (WB-67D) would be theappropriate design vehicle are limited
Has less offtracking and swept path width than WB-19 (WB-62) andWB-20 (WB-65 and WB-67) which operate on similar roads
Retain because represents maximum vehicle size limit specified
in Federal law
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
19/30
Double-Trailer: WB-23D (WB-77D)
If current freeze on size and weight limits were lifted, a
combination with 10.1 m (33 ft) trailers could be legalized
TRB Special Report 267 recommends such a combination Not recommended for inclusion as design vehicle at present time
Appropriate design vehicle developed for future consideration should
such a truck become legal and common
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
20/30
Double-Trailer: WB-33D (WB-109D)
Also referred to as turnpike double
Consists of tractor with two 14.6 m (48 ft) trailers Operate under permit on specific roads
May be appropriate design vehicle on roads wherethey operate in substantial numbers
Current design vehicle uses a cab-over tractor Conventional tractor would be more realistic
Larger wheelbase of conventional tractor would haveminimal effect on offtracking
No recommended changes to current WB-33D (WB-109D) design vehicle
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
21/30
Double-Trailer: WB-37D (WB-120D)
If current freeze on size and weight limits were lifted, a
combination with 16.2 m (53 ft) trailers could be of interest
Economically advantageous to move low density commodities
Not recommended for inclusion as design vehicle at present time
Appropriate design vehicle developed for future consideration should
such a truck become legal and common
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
22/30
Double-Trailer: WB-28D (WB-92D)
Rocky Mountain doubles are fairly common in 20 states
Cross between the twin-trailer and turnpike double
May offtrack more than other relatively common truck types Recommended for inclusion in Green Book
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
23/30
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
24/30
Triple-Trailer: WB-30T (WB-100T)
Consists of three 8.7 m (28.5 ft) trailers
One semitrailer and two full trailers
Represents most common triple-trailer combination on road
No recommended changes to this design vehicle
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
25/30
Summary of Design Vehicle
Recommendations
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
26/30
Single Unit Trucks
Retain current 2 axle SU
Designate as SU-6 (SU-20)
Add longer 3 axle SU
Designate as SU-8 (SU-25)
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
27/30
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
28/30
Double-Trailer Combinations
Retain current WB-20D (WB-67D) with 8.7 m (28.5 ft) trailers
Configuration specified in Federal law WB-23D (WB-77D) with 10.1 m (33 ft) trailers developed for
future consideration
Retain current WB-33D (WB-109D) with 14.6 m (48 ft) trailers
(i.e., turnpike double) WB-37D (WB-120D) with 16.2 m (53 ft) trailers developed for
future consideration
Add WB-30D (WB-92D) with 14.6 m (48 ft) semitrailer and
8.7 m (28.5 ft) full trailer (i.e., Rocky Mountain double)
WB-23BD (WB-75BD) developed for future consideration
(i.e., B-train double)
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
29/30
Triple-Trailer Combinations
Retain current WB-30T (WB-100T) with 8.7 m
(28.5 ft) trailers
-
7/27/2019 05_5_Torbic_RecommendedChangesInFutureDesignVehicles
30/30
Questions???