Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Report
developing performance measures and setting goals logically follow from needs of stakeholders
identified earlier in this report and take into account the data limitations in developing statistics
describing those performance characteristics.
Types of Goals
As noted previously, the challenge is not which measures to use, but how to set the standards for
judging performance. To do that, it is important to clearly define and evaluate the intended
outcome. After all, performance measures are developed to assist in the achievement of specific
outcomes: what are the types of outcomes desired by transportation agencies? A review of
currently used transportation agency performance goals shows that “intended outcomes” can be
grouped into three basic categories:
• Improve current performance to meet a technical standard of excellence or “optimal”
level in important areas.
• Challenge an agency to “stretch” to make dramatic improvements in some area.
• Report current performance in areas where “truly good” performance cannot be obtained
because of circumstances beyond the control of the agency.
Engineering Optimal Goal
At first blush, the first of these performance-goal categories would seem the obvious choice for
engineers. For example, we might set a roadway reliability goal of having “roadways operate at
the speed limit 95% of the time,” given the obvious positive implications for both passenger and
freight travel.
Unfortunately, the technical difficulties of meeting such a standard in currently congested urban
areas make the adoption of such a goal infeasible. In economic terms, the cost of achieving such
a goal is not worth the benefits obtained. This is why a more-modest goal of “operating the
freeways at no slower than the point at which they can carry maximum vehicle throughput” has
been adopted in several metropolitan regions around the country. For example, the North
Carolina Department of Transportation (NCDOT) "2009-2010 Executive Organizational
Performance Measures and Targets" (8) report defines performance measure 2.5 as "Percent
reduction in expected growth of commuter generated vehicle miles traveled due to transportation
options” as “Greater than 25%” In other words, NCDOT decided that they could not expect to
control growth and VMT, but they could potentially lower the expected increase. WSDOT has
adopted a congestion management guideline that uses maximum throughput productivity as a
basis for congestion mitigation measures.
The major challenge of adopting “obvious” performance goals occurs when a goal that can be
agreed to easily by users is unrealistic in terms of what the transportation system can provide.
When this happens, the providing agency is placed in the very difficult position of publically
failing to achieve its goals or even to make substantial progress toward achieving those goals.
For a public agency that can be easily attacked in the news media, adopting a performance goal
that makes it look bad, no matter what it does, is something to be avoided at all costs. Therefore,
it is important that the performance goals be selected after considering whether the intended
outcomes are reasonable.
Two examples of public agencies that had to back off quantitative goals illustrate the challenges
of goal setting. A recent one, which is probably also the best known, involved the Minnesota
Department of Transportation (MnDOT). MnDOT deployed a large number of ramp meters in
the Twin Cities area and operated them in a manner that gave priority to freeway traffic flow in
GOALS AND PERFORMANCE TARGETS Page 33