Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Report
fluctuations in normal traffic/special events are expected to be increasingly frequent sources of
congestion due to the increase in the variation of day-to-day travel demand, resulting from
population growth and relaxation of economic constraints on travel. The economic and
environmental conditions in the pessimistic scenario along with reduced travel demand will most
likely increase delay due to weather and work zones. Increases in the frequency of rare events such
as tornados, snow storms, and flooding will be responsible for infrastructure failure and
interruptions.
Improving agency management, organization, and resource allocation will become increasingly
more important in any of the future scenarios, given that each scenario is expected to have high
impacts from more than one source of congestion. Therefore, the SO&M structures within agency
organizations will need to be better balanced in the future to provide both travel time reliability
and infrastructure improvements.
Given the impact of the future scenarios on the sources of congestion, specific treatments from
Chapter 6 are listed for each future scenario in Table 7.2. The list should be viewed as an example
combination of treatments to improve travel-time reliability under each of the three alternative
futures. This assignment should not be understood as an exclusive set of treatments, but as a
directory of the treatments that will be most effective, given the characteristics of each scenario.
The treatments not listed should not be discarded by agencies, since all of the treatments listed in
this report can continue to improve travel-time reliability. To better understand the logic behind
Table 7.2, the examples below illustrate the applied methodology:
• In Table 7.2, under the Traffic Incidents source of congestion, Transportation Management
Center (TMC) was assigned to the baseline scenario, since it is currently implemented, as
well as to the optimistic and mediocre scenarios (ranked as high and medium in Table 7.1).
Even though the TMC treatment was not assigned to the pessimistic scenario that does not
mean that it will not be used under this scenario. The correct interpretation is that under the
optimistic and mediocre scenarios, there is a greater need to expand the TMC strategy
(given the characteristics of each scenario) while under the pessimistic scenario the strategy
usage will remain about the same when compared to the baseline conditions.
• Under the Weather source of congestion, National Traffic and Road Closure Information
was identified in the baseline and pessimistic scenarios. For this specific treatment, the
proper interpretation is that it is being actively used today, but due to the higher number of
disruptions related to recurrent weather events in the pessimistic scenario, the expansion of
this treatment will be critical to keep roadway users informed about traffic, roadway
conditions, and safety.
• The third example explains the logic behind the Signal Retiming and Optimization (SRO)
treatment under the Traffic Control Devices source of congestion. SRO was assigned to the
baseline and to all future scenarios due to its effectiveness in mitigating delays at signalized
intersections. The relatively low cost associated with this treatment makes it essential to
improve travel-time reliability in all three future scenarios.
• The last example applies to Vehicle Infrastructure Integration (VII). Under the Fluctuations
in Normal Traffic/Special Events source of congestion, VII is only identified for the
optimistic scenario. Since it is a set of technologies that is still being tested, its application
was not assigned to the baseline scenario. Due to the increased level of technological
A CONCEPT OF OPERATIONS Page 109