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Publication Number: FHWA-HRT-12-054
Date: December 2012

 

Methodologies to Measure and Quantify Transportation Management Center Benefits: Final Synthesis Report

2. TMC Functions and Examples of Performance Evaluation

2.1 TMC Functions

The goals and initiatives established by agencies determine the TMC functions and the measures that evaluate these functions. Appendix A provides one agency's flow sequence for this process.

Table 1 identifies many of the possible functions of TMCs by the types of facilities managed. In later sections of this report, these functions are related to performance measures and the data and parameters needed to implement those measures.

2.2 Examples of Performance Evaluation Systems

Performance evaluation systems may take either of the following forms:

Performance evaluation systems may include the archived data user service functions of the National ITS Architecture.(2)

Table 2 provides key functional characteristics for several performance evaluation systems.

Table 1. TMC functions.

TMC Functions Facilities Managed by TMC Comments
Freeways Signal Systems and Surface Streets Corridorsa Special Facilitiesb
Active Traffic Managementc X   X X See reference 3.
Speed harmonization X     X  
Temporary shoulder use X     X  
Queue warning X     X  
Dynamic truck restrictions X     X  
Dynamic routing X   X X  
Dynamic lane markings X     X  
Data Analysis and Warehousing X X X X These are support functions. They relate to outputs rather than to outcomes. No measures are provided for these functions in section 3.
Incident Response          
Development of incident management plans X X X X  
Selection of incident management plan X Where TMCs have this responsibility X X  
Assistance to emergency service providers X   X X  
Maintenance         These are support functions. They relate to outputs rather than to outcomes. No measures are provided for these functions in section 3.
Maintenance of TMC facilities X X X X  
Management of field equipment maintenance X X   X Field equipment maintenance management for corridors depends on division of responsibilities.
Configuration management of TMC and ITS facilities X X X X  
Coordination of roadway maintenance and construction X X   X  
Motorist Information          
Management of information for ITS field devices X Where agency operates devices X X  
Provision of information to external services   Sometimes      
Planning X X X X These are support functions. They relate to outputs rather than to outcomes. No measures are provided for these functions in section 3.
Ramp Management and Conventional Lane Management          
Ramp metering X   X X  
Ramp closure X   X X  
Conventional lane controls X X X X  
Security         These are support functions. They relate to outputs rather than to outcomes. No measures are provided for these functions in section 3.
Security in TMC X X X X  
Security of ITS field devices Possibly Not often Possibly Usually  
Other security functions Possibly Not often Possibly Usually Security monitoring of other transportation department facilities.
Service Patrol X     X  
Signal Timing          
Signal timing plan development   X Seed    
Signal timing operations management   X Seed    
Emergency vehicle signal preemption   X Seed    
Special Functions         These are support functions. They relate to outputs rather than to outcomes. No measures are provided for these functions in section 3.
Roadway ventilation       X See reference 4.
Roadway fire detection and suppression       X See reference 4.
Other Supervisory Control and Data Acquisition Functions       X May include pumping, electrical system control, and motorist telephone system.(4)
Training and Support X X X X These are support functions. They relate to outputs rather than to outcomes. No measures are provided for these functions in section 3.
Transit Assists          
High occupancy vehicle (HOV) bypass of metered lanes X   X X  
Transit signal priority   X Seed    
Weather Monitoring X Not usually X X  

a Includes TMCs with responsibility for operations on alternate routes.

b Includes bridges and tunnels.

c Active traffic management includes speed harmonization, temporary shoulder use, queue warning, dynamic merge control, construction site management (active traffic management methodologies), dynamic truck restrictions, dynamic routing and traveler information, and dynamic lane markings. Separate lines will be provided for each strategy.

d Responsibility for timing plan development and operations rests with the agency responsible for traffic signal systems. This function is applicable when freeway and signal system TMCs share a common facility.
Note: Blank cells in the comments field indicates no comment was provided.

Table 2. Characteristics of representative ITS performance evaluation systems.

System Key Data Processing Features Data Collection Periods Data Source Key Measures Provided
California Department of Transportation (Caltrans) Freeway Performance Measurement System (PeMS)(5,6)
  • Detects and corrects missing and bad data through imputation techniques.
  • Computes speed by means of g factor calculations.a
  • Estimates truck volumes.
Collects data at 30-s intervals, then aggregates to 5-min and hourly periods.
  • Inductive loop detectors, generally single loop detectors in each lane.
  • Incident data from California Highway Patrol. Weather data.
Volume, occupancy, speed, congestion delay, vehicle miles traveled (VMT), and travel times.
Washington State Traffic Data Acquisition and Distribution System
  • Contains flags to alert users to suspect data.
  • Uses ladder algorithm to compute travel time.b
Collects data at 20-s intervals, then aggregates to 5-min data.
  • Inductive loop detectors, generally single loop detectors in each lane. Some stations have loop traps. Automatic vehicle location data.
Volume, occupancy, speed, travel time, and travel time reliability.
Minnesota TMC(7)
  • Contains flags to alert users to suspect data.
Collects data at 20-s intervals, then aggregates to 5-min data.
  • Single inductive loop detectors in each lane.
 
Florida Statewide Traffic Engineering Warehouse for Regional Traffic Data (STEWARD); designed as a statewide system that links to each district(8)
  • Strong integration with roadway and detector characteristics
  • Data completeness test
  • Data threshold checks.
Collects data at 20-s intervals, aggregates to 5-, 15-, and 60-min periods.
  • Mainline and ramp detectors.
  • Adaptable to all detector types.
Volume, occupancy speed, lane volume balance, effective vehicle length (see section 5.1.2.1), input/output balance, VMT, vehicle hours, delay, kinetic energy, and level of service.

a Additional information is provided in table 22.

b The g factor represents the effective length of the vehicle at the tuning of the loop detector. It varies over the course of time. An algorithm is in PeMS to calculate the g factor as a function of time.
Note: Blank cell indicates no key measures were provided.

 

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