Transportation Research Board Planning Applications Conference, May 2007 Given by: Ronald T. Milam, AICP Contributing Analysts: David Stanek, PE Chris Breiland Mike Iswalt The Secrets to HCM Consistency Using Simulation Models

Typical Simulation Examples

When to Use Simulation

When vs. How? The HCM methodologies may not be appropriate in environments with multiple travel modes or multiple hours of congestion. “… the HCM methods are generally not appropriate…for the evaluation of queues that are building over both time and space.” – Page 9-1, HCM 2000 “ Certain freeway traffic conditions cannot easily be analyzed by the methodology. Multiple overlapping bottlenecks are an example. Therefore, other tools may be more appropriate…” - Page 22-1, HCM 2000

Challenges/Issues Multiple software packages AIMSUN CORSIM Dynasim Paramics SimTraffic TransModeler VISSIM others… Which ones are HCM consistent? How can a user or reviewer be sure?

Traffic simulation programs provide many performance measures Total delay Density Travel time Average speed Travel distance Number of stops However, the definition of the performance measures may differ from the HCM definition. Stopped delay Throughput Emissions Fuel consumption Queue length Others Simulation Performance Measures

HCM Performance Measures HCM methods determine LOS for facility types based on different performance measures Facility Type Intersections Urban Streets Two-Lane Highways Multi-lane Highways Freeways Performance Measure Control Delay Speed Percent Time Spent Following Density

Roadway System Peak hour factor Intersections Defining the intersection approach Freeways Ramp influence areas Consistency Issues

Peak Hour Factor HCM defines the LOS for the peak 15 minutes of the peak hour Peak Hour Peak 15-Minute Volume Peak Hour Volume

Edit the periods file to create 15-minute interval demand periods. Peak Hour Factor, continued… Paramics Example

Use the divisor parameter in the demands file to adjust peak hour volumes. Hourly data with PHF of 0.95 implies a divisor of 3.8. Peak Hour Factor, continued… Paramics Example

Include delay for all vehicles on approach Model link delay may not include entire intersection approach Model Network Maximum Queue Intersection Approach Delay

Intersection Approach Delay, continued… SimTraffic Example Upstream unsignalized intersection divides the southbound approach into two links.

Intersection Approach Delay, continued… Unsignalized Driveway Intersection Signalized Intersection Link 1 Link 2 SimTraffic Example

Output report for signalized intersection shows delay for Link 1 only. Intersection Approach Delay, continued…

SimTraffic Example Adding delay for Links 1 and 2 to get the entire southbound approach delay. LOS ResultsLink 1Links 1 & 2 SB Approach E / 59F / 86 IntersectionD / 40D / 44 Intersection Approach Delay, continued…

HCM defines the ramp merge analysis area as the two right shoulder lanes plus the auxiliary lane for 1,500 feet downstream of the ramp gore Ramp influence area does not necessarily match model links Ramp Influence Area

Build model network to account for ramp influence area and volume collection locations. Ramp Influence Area, continued… VISSIM Example

Ramp merge area with acceleration lane 450 ft Ramp Influence Area Ramp Influence Area, continued… Link 190 Link 191 2,930 ft On-Ramp

Collect statistics for ramp influence area. 450 ft 1,050 ft Ramp Influence Area, continued… VISSIM Example

Collect statistics by lane for each link. Ramp Influence Area, continued… VISSIM Example

Calculate volume-weighted average density first across links, then across lanes Ramp Influence Area, continued… Across Links Across Lanes VISSIM Example

Analysis Results LocationDensity (vpmpl)LOS Link 190 (all lanes) 42.4E Link 191 (all lanes)37.2D Ramp Influence Area42.1E Ramp Influence Area Ramp Influence Area, continued… VISSIM Example Link 190 Link 191

FHWA - Modify NGSIM priorities to better reflect user needs TRB - Update the HCM to provide specific guidelines for simulation software vendors and to reflect a wider range of performance measures Software Vendors – Provide technical support and training on HOW to perform simulation modeling Users – Invest time to understand HOW to perform simulation modeling Recommendations

Questions? The Secrets to HCM Consistency Using Simulation Models