Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Report
These data allow actual performance of the roadway to be compared against the performance
expected from the implemented traffic management plans in order to determine the performance
of those control plans and the need for changes to those plans.
Bottlenecks
Specific reporting statistics describing bottlenecks are not recommended in this report. However,
the performance data of a roadway operating agency can help identify and understand the causes
of bottleneck locations on the roadways.
Information Dissemination
The third category of performance measures deals with improving the passenger traveler and
shipper experience and with decreasing the costs associated with unreliable travel conditions.
Regardless of how well an agency (or group of agencies) responds to disruptions of any kind,
disruptions will continue to occur in the future. Through the stakeholders meetings, it was
confirmed that both passenger travelers and freight movers understand that some level of
unreliability will exist on the roadway system as a result of unavoidable disruptions. However,
there was near-unanimous agreement that having ready access to information on expected travel
conditions is essential in reducing the actual costs imposed by those “slower than desired”
conditions. Travelers would gain considerable benefit by having improved access to accurate
descriptions of expected travel conditions. To improve their travel decisions and minimize the
costs associated with unavoidable delays, both passenger travelers and freight movers require
better access to accurate predictions of expected travel times and conditions.
The expected travel times can be calculated from the same data that are used to develop the
performance statistics described previously. Once that has been done, the key is to use a variety
of applicable mechanisms to make those predictions easily accessible to the public. Regardless of
the accuracy of “average” expected conditions calculated from historical data, actual roadway
performance will vary from the expected norm because of the occurrence of unexpected or
unplanned disruptions (e.g., accidents). Having information about these disruptions and their
expected effects on travel times is essential in improving both the decision-making and the
satisfaction levels of travelers. It also reduces (but does not eliminate) the costs that these
disruptions impose on travelers. Therefore, a second key aspect of the traveler-information
system desired by all of the “stakeholder customers” interviewed is a fast and accurate process
for updating their knowledge of current travel conditions. This requires both an effective system
for identifying travel disruptions as they occur and good predictive algorithms for estimating the
effects that those disruptions will have on expected travel times. Once updated travel conditions
are available, it is necessary to have a variety of effective delivery mechanisms for
communicating the newly computed “expected conditions” to all interested travelers.
In response to stakeholder input, the following performance measures describe the types of
information that are most useful:
• The percentage of freeway center-line miles for which real-time traveler information is
available;
• The percentage of arterial center-line miles for which real-time traveler information is
available;
GOALS AND PERFORMANCE TARGETS Page 31