Download - Lexington Area TransCAD Travel Demand Model
Lexington Area TransCADTravel Demand Model
July 22, 2003
Kentucky Traffic Model Users Group Meeting
Kyeil Kim, Ph.D.
Bernardin, Lochmueller & Associates, Inc.
Main Features
Consists of separate time-of-day (TOD) models Realistic free-flow speed based on a speed survey and
HCM-based signal delays Varying capacities by TOD for reversible lanes Model parameters are based on recent travel survey and
KYTC’s HIS database. 2-stage assignments: Initial and Feedback User-friendly model GUI
Model Area
Roadway Network
Incorporation of KYTC’s HIS and geometric/operations data
All MINUTP network attributes
FHWA functional class, posted speeds, etc.
Number of lanes, reversible lanes & bike lanes
Area type, shoulder widths, median type, etc.
Traffic signals & multi-way stops (signal priority, multiple signals)
Turn prohibitors
TAZ DB
Total 489 zones Internal zones = 445 zones External zones = 44 zones
51 data attributes Date related to population and household Employment by SIC code Student population, group quarters & school enrollment Vehicle ownership
Key data for estimating trip productions and attractions
Speed/Capacity Estimation
Free-flow speed, peak-hour capacity & daily capacity
A special GIS-dk program to estimate directional capacities by TOD & free-flow speed
Consideration of changes in reversible lanes by TOD
Free-flow speed = f (functional class, posted speed, number of lanes, facility type, delays on interrupted facilities)
Daily capacity = f (functional class, number of lanes, facility type)
Peak-hour capacity = max. service flow * adjustment factors
where, Adjustment factors = f (geometric data, functional class, facility type, area type, delays on
interrupted facilities)
Speed/Capacity Estimation (Cont’d)
Delays on interrupted facilities
HCM 2000 procedure
delay/veh = uniform delay * PF + incremental delay + initial queue delay
where, PF = progression factor = f (arrival type, g/C)
uniform delay =
Varying g/C’s and PF’s by signal priority and multiple signals
Cgcv,1min1
Cg1C5.0 2
Lexington ModelGUI
Lexington ModelGUI
Trip Generation
Six internal trip purposes: - HBW, HBK12, HBU, HBO, NHBW & NHBO
Trip production
- Cross-classification technique
- Data: The 2000 Knoxville Household Travel Behavior Study, The 1999 Indiana University Travel Demand Survey
- Analysis of Variance (ANOVA) and non-parametric correlations techniques to identify the predictor variables for various trip
purposes
- Stratification curve: distribution of households in a zone over various
levels of the predictor variables
Trip Generation (Cont’d)
Trip production model
Trip Purpose 1st Predictor 2nd Predictor Overall Trip Rate
HBW Workers/H.H. Vehicles/H.H. 1.30
HBK12 Students/H.H. None 0.64
HBU University Student/TAZ
None 0.48
HBO Household Size Vehicles/H.H. 3.72
NHBW Workers/H.H. Household Income
0.84
NHBO Household Size Vehicles/H.H. 2.02
Total 9.00
Trip Generation (Cont’d)
Trip attraction model: the Atlanta regression model
Trip Purpose Independent Variable Parameter
HBW Total Employment 1
HBK12 K-12 Enrollment 1
HBU University Enrollment 1
HBO
Population .1168Retail Employment .8257
Commercial & Gov’t Employment .0408Other Employment .0137
NHBW & NHBO
Population .0575Retail Employment .7593
Commercial & Gov’t Employment .0846Other Employment .1053
Trip Distribution
Doubly-constrained Gravity model for the 6 internal trip purposes & E-I trips
Friction factors
- Initial factors from the old MINUTP model
- Fitting to Gamma function for smoothing the factors
- Adjustment of Gamma parameters to arrive at correct trip lengths by trip purpose
Socioeconomic (or K) factors
Vehicle Occupancy
Vehicle occupancy rates by trip purpose
HBW 1.09 persons/vehicle
HBK12 1.96 persons/vehicle
HBU 1.20 persons/vehicle
HBO 1.83 persons/vehicle
NHBW 1.17 persons/vehicle
NHBO 1.75 persons/vehicle
(Source: The 2000 Knoxville Household Travel Behavior Study)
Time-of-Day
AM peak (06:30~09:00); Midday peak (12:00~13:30); PM peak (15:30~18:00) and Off-peak
TOD factors
- Split the 24-hr trip table into tables by TOD
- by trip purpose
Directional factors
- Convert trip tables in a production-attraction format to origin-destination tables
- by trip purpose and by TOD
Data Source: the 2000 Knoxville Household Travel Behavior Study
External Trips
44 external stations
E-E trips The 1994 O-D survey by Wilbur Smith Associates Most of E-E trip interchanges except for the interstate and US60 exchanges
Kentucky Statewide Travel Model via critical link analysis E-E trip interchanges for the interstate and US60 external stations
Modlin Equations A check of reasonableness
E-I trips = ADT’s - E-E trips at each external station
27 stations of the 44 stations carry through trips
Traffic Assignment
Time-of-day user equilibrium assignments
- separate AM-peak, Midday-peak, PM-peak & Off-peak assignments
Improved free-flow speeds and varying capacities by TOD by reversible lanes
Separate volume-delay functions (defaults)
Unsignalized facilities = 0.20; = 10.0
Signalized facilities = 0.05; = 10.0
Feedback assignment
Feedback Loop24-Hour
Average SpeedGravity Model
TOD Trip TableFactoring
AM-peakAssignment
Midday-peakAssignment
PM-peak Assignment
Off-peakAssignment
24-Hour Weighted Average
Congested Link Speed
CAL_REP
Assignment post-processor written in GIS-dk and incorporated in the GUI
Various error statistics by functional classification, volume group, screenline, cutline and specific corridors
Error statistics
total counts, average counts, counts standard deviation total loadings, average loadings, loadings standard deviation % root mean square error mean error, % error total counts VMT, total loadings VMT, % VMT error
Assignment Results
CAL_REP Report
Loading % error = -1 % Loading VMT error = 0.9% % RMSE = 25% Interstate =
0.03% (% error); -2.6% (VMT error) Urban Principal Arterial =
-1.3%; -3.1% Urban Minor Arterial =
-3.8%; 3.7%
In Progress
Model runs for future years and post-processing 2030 with committed projects only
2010 with committed plus Plan projects scheduled for completion by 2010
2020 with committed plus Plan projects scheduled for completion by 2020
2030 with all projects in the current LRP
“Multinet” feature in GUI for efficient network data handling
THANK YOU!