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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

3. Performance Measures

Two general types of measures may be considered: outcome-oriented and output-oriented.

Outcome-oriented measures are likely to be of interest to highway users and high-level decisionmakers because they include universally high-priority issues such as delay and safety. Measures that are components of a benefit-cost analysis are also outcome measures.

Output-oriented measures are the direct result of actions taken by the TMC. These outputs, in turn, result in outcomes. An extensive description of both outcome and output measures is provided by Park.(9)

Many TMCs utilize measures of outputs and outcomes, although the specific measures used vary among TMCs. The number of incident management-related messages is an example of an output measure.

Park and Shaw are key sources for descriptions of numerous measures.(9,10) For this study, researchers selected measures that were considered to be most useful. While the focus was on outcome-oriented measures, a number of commonly used output measures were included as well. The criteria for measure selection included the following:

Table 3 describes criteria that may be used to evaluate measures.(10)

Table 3. Comparison of performance measures criteria.

General Criteria Specific Criteria
Clarity and simplicity The measure is simple to present, analyze, and interpret.
The measure is unambiguous.
The measure's units are well defined and quantifiable.
The measure has professional credibility.
Technical and nontechnical audiences understand the measure.
Descriptive and predictive ability The measure describes existing conditions.
The measure can be used to identify problems.
The measure can be used to predict change and forecast conditions.
The measure reflects changes in traffic flow conditions only.
Analysis capability The measure can be calculated easily.
The measure can be calculated with existing field data.
There are techniques available to estimate the measure.
The results are easy to analyze.
The measure achieves consistent results.
Accuracy and precision The accuracy level of the estimation techniques is acceptable.
The measure is sensitive to significant changes in assumptions.
The precision of the measure is consistent with planning applications.
The precision of the measure is consistent with an operation analysis.
Flexibility The measure applies to multiple modes.
The measure is meaningful at varying scales and settings.

Figure 1 shows the Texas Department of Transportation's (TxDOT) balanced scorecard approach to developing performance measures.(10) Agencies often define measures for highway system operations. While these operations may include TMCs, they usually cover the more general functions of the highway network, such as the measures used by the Florida Department of Transportation (FDOT), which are shown in table 4.(9)

Figure 1. Illustration. TxDOT balanced scorecard approach. This figure shows a two-axis quadrant system of the Texas Department of Transportation (TxDOT) balanced scorecard approach to developing performance measures. The positive y-axis is labeled External, and the negative y-axis labeled Internal. The positive x-axis is labeled Results, and the negative x-axis is labeled Process. The quadrant between External and Results is labeled Outcome, the quadrant between Results and Internal is labeled Output, the quadrant between Internal and Process is labeled Efficiency, and the quadrant between Process and External is labeled Explanatory.

Figure 1. Illustration. TxDOT balanced scorecard approach.

Shaw and Park provide extensive discussions of measures used by agencies as well as the equations and computational procedures that may be used to develop several of these measures.(10,9) While many agencies employ these general techniques, the specific schemes used often differ.

Table 4. Measures used by FDOT.

Dimension of Mobility

Mobility Performance Measures

State Highway System

Florida Intrastate Highway System

Florida Intrastate Highway System Corridors

Metropolitan Highway Systems

Definitiona

Quantity of travel

Person miles traveled (PMT)

X

X

X

X

Average annual daily traffic (AADT) x length x vehicle occupancy

Truck miles traveled

X

X

X

X

AADT x length x percent trucks

VMT

X

X

X

X

AADT x length

Person trips

       

Total person trips

Quality of travel

Average speed

X

X

X

 

Average speed2 weighted by PMT

Delay

X

X

X

X

Average delay

Average travel time

   

X

 

Distance ¸ speedb

Average trip time

     

X

Door to door trip travel time

Reliability

   

X

X

Percent of travel times that are acceptable

Maneuverability

   

X

 

Vehicles per hour per lane

Accessibility

Connectivity to intermodal facilities

X

X

X

X

Percent within 5 mi
(1 mi for metropolitan)

Dwelling unit proximity

 

X

X

X

Percent within 5 mi
(1 mi for metropolitan)

Employment proximity

 

X

X

X

Percent within 5 mi
(1 mi for metropolitan)

Industrial/warehouse facility proximity

 

X

   

Percent within 5 mi

Percent miles bicycle accommodations

X

   

X

Percent miles with bike lane ¸ shoulder coverage

Percent miles pedestrian accommodations

X

   

X

Percent miles with sidewalk coverage

Utilization

Percent system heavily congested

X

X

X

X

Percent miles at level of service (LOS) E or Fc

Percent travel heavily congested

X

X

X

X

Percent daily VMT at LOS E or F

Vehicles per lane mile

X

X

X

X

AADT x length ¸ lane miles

Duration of congestion

X

X

X

X

Lane-mile hours at LOS E or F

a Definitions shown are generally for daily analysis. Calculations for the peak are based on prevailing conditions during the typical weekday 5 to 6 p.m. peak.
b Speed based on models using the Highway Capacity Manual or field data.(4)
c LOS ratings are determined using the Highway Capacity Manual.(4)

This project focuses on influencing the development, use, and implementation of performance measures, data collection and management, monitoring, evaluation of effectiveness, and reporting on the benefits of TMCs and their traffic management-related functions and services. [1] Therefore, this report frames this information in a way that provides agencies that currently have management systems but that do not have a robust evaluation methodology with specific data structures, including algorithms and computational procedures, that will allow them to compute measures that satisfy their needs and objectives.

This project includes measures that may be used to provide monetary benefits for a benefit-cost analysis. The classes of monetary benefits resulting from ITS improvements and a typical breakdown for those benefits on an urban freeway are shown in table 5.

Table 5. Example of percentage of ITS monetary benefits for benefits classes.(11)

Benefit Class Benefit Percentage
Private vehicle occupant delay 66.1
Commercial vehicle occupant delay 4.3
Cost of crashes 13.1
Value of delay for goods 8.0
Fuel cost of delay 8.6
Total 100

* Indicates measures used for benefit-cost analysis.
Note: Blank cells in the “Sub-Measure� column indicate that no sub-measure was identified.

Table 6 provides a representative set of measures that may be used for an ITS performance evaluation. Table 7 relates the outcome-oriented TMC functions in table 1 to the measures in table 6.

Table 6. Measures of effectiveness.

Type of Measure Sub-Measure Identifier Quantity Measures or Description Benefit-cost Analysis Traffic Flow Quality and Safety Measures Benefits Perceived by the Public Measure for TMC Operations Performance
System delay measures Vehicle system delay* D.1 Vehicle hours per year; archived on a link, ramp, and intersection basis and aggregated to the system level X X X X
Private passenger vehicle occupant delay* D.2 Person hours per year X X X  
Commercial vehicle occupant delay* D.3 Person hours per year X X X  
Goods inventory delay* D.4 Ton hours per year X      
Transit vehicle occupant delay D.5 Person hours per year X   X  
Safety Freeway crashes* S.1 Crashes per million VMT per year; archived on a link and ramp basis and aggregated to the system level X X   X
Secondary crashes S.2 Crashes per million VMT per year   X   X
Crashes at intersections* S.3 Crashes per million vehicles entering intersection X X   X
Property damage only (PDO) crashes S.4 Crashes per million VMT per year X X   X
Safety (continued) Fatal crashes S.5 Fatal crashes per million, VMT, and fatal crashes per
1 million vehicles entering intersection
X X   X
Injuries resulting from crashes S.6 Injury crashes per million, VMT, and injury crashes per 1 million vehicles entering intersection X X   X
Work zone related crashes S.7 Work zone crashes for the TMC coverage region   X   X
Pedestrian crashes S.8 Pedestrian injuries/deaths per 1 million vehicles entering intersection   X   X
Safety performance index S.9 Weighted crash frequency and severity   X   X
Fuel consumption*   F Gallons per year X   X  
Throughput Freeway throughput T.1 VMT per year during peak hour   X    
Intersection throughput T.2 Vehicles per peak hour at an intersection   X    
Emissions   E Kilograms per year for each emission constituent        
Service quality/user perceptions Route travel time Q.1 Peak hour route travel time (hours)   X X X
Route travel time reliability Q.2 Buffer index, planning time index   X X X
User satisfaction Q.3 User satisfaction scales and surveys     X X
User satisfaction Q.4 Complaints received by agency     X X
Equity User perception U.1 User complaints received by agency     X X
Gini coefficient or Lorenz curve U.2 Users relatively disbenefitted per total users        
Service patrol measures Service patrol assists M.1 Assists per year     X X
Quality of service M.2 Patrol coverage periods (hours per year)     X X
Quality of service M.3 Average motorist waiting time (minutes)     X X
Quality of service M.4 Extent of roadway serviced (centerline miles)     X X
Rating by public M.5 Rating scale     X X
Incident clearance time Average incident clearance time C Annual average incident clearance time for moving lanes minutes X     X
Response to weather situations Response time to provide actionable information to motorists W Average time in minutes from receipt of information by Road Weather Information Systems or other means to provide motorist information and to provide information to other response services   X X X
Life-cycle cost*   P Dollars per year X     X
Database to provide motorist information See section 5.9 I Rating scales   X X X

* Indicates measures used for benefit-cost analysis.
Note: Blank cells in the "Sub-Measure" column indicate that no sub-measure was identified.

Table 7. Relationship of TMC functions to measures of effectiveness.

Type of Measure Sub-Measure Identifier TMC Functions
Active Traffic Management Incident Response Motorist Information Ramp Management and Conventional Lane Management Service Patrol Signal Timing Transit Assists Weather Monitoring
System delay measures Vehicle system delay* D.1 X X X X X X X X
Private passenger vehicle occupant delay* D.2 X X X X X X   X
Commercial vehicle occupant delay* D.3 X X X X X X   X
Goods inventory delay* D.4 X X X X X X   X
Transit vehicle occupant delay D.5 X X X X X X X X
Safety Freeway crashes* S.1 X X X X X     X
Secondary crashes S.2 X X X X X     X
Crashes at intersections* S.3     X     X   X
PDO crashes S.4 X X X X X X   X
Fatal crashes S.5 X X X X X X   X
Injuries resulting from crashes S.6 X X X X X X   X
Work zone related crashes S.7 X X X X X     X
Pedestrian crashes S.8                
Safety performance index S.9 X X X X X X   X
Fuel consumption*   F X X X X X X X X
Throughput Freeway throughput T.1 X X X X X     X
Intersection throughput T.2           X   X
Emissions   E X X X X X X X X
Service quality/user perceptions Route travel time Q.1 X X X X X X X X
Route travel time reliability Q.2 X X X X X X X X
User satisfaction Q.3 X X X X X X   X
User satisfaction Q.4 X X X X X X   X
Equity User perception U.1       X     X  
Gini coefficient or Lorenz curve U.2       X     X  
Quality of assistance to motorists Service patrol assists M.1         X      
Quality of service M.2         X      
Quality of service M.3         X      
Quality of service M.4         X      
Rating by Public M.5         X      
Incident clearance time Average incident clearance time C X X X X X     X
Response to weather situations Response time to provide actionable information to motorists W X X X X   X   X
Life-cycle cost*   P X X X X X X X X
Database to provide motorist information See section 5.6 I X X X         X

* Indicates measures used for benefit-cost analysis.
Note: Blank cells in the "Sub-Measure" column indicate that no sub-measure was identified.


1 Review the scope of work for this report for additional information.

 

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