Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Report
well as to generate funds needed for operating, maintaining, and improving the transportation
system.
The second category includes actions to increase roadway capacity, such as:
• expansions or additions to highway facilities
• the application of better operational and technical systems to maximize the performance of
existing infrastructure
• advances in technology and procedures that more quickly restore capacity that has been
lost as a result of disruptions (incidents, bad weather, work zones)
• the optimal use of existing transportation system capacity controlled by other transportation
agencies, firms, or individuals (This can be accomplished by providing incentives for mode
shifts from single-occupant vehicles to multi-occupant vehicles and more effective use of
alternative rights-of-way.)
The types of solutions that can be brought to bear on the demand/capacity imbalance depend on
whether congestion can be anticipated or results from unexpected events. Where volume routinely
approaches and/or exceeds capacity (recurring congestion), demand management and capacity
increases are likely to be effective in improving reliability. In locations where unexpected
disruptions cause the majority of congestion, techniques that detect disruptions and facilitate rapid
recovery from those events are more likely to be effective. Even in situations where unexpected
disruptions cause the majority of congestion, however, demand management and/or capacity
increase strategies will also warrant consideration since their effect is to create a capacity margin
that helps assure the system’s resilience in effectively responding to unexpected events.
IMPROVED TRAVEL-TIME RELIABILITY: WHAT’S NEEDED?
The most significant benefits in improving travel-time reliability will be attained when
technological changes, operational solutions, and organizational actions are used in an integrated
fashion to improve the balance between travel demand and capacity.
A variety of technological changes, operational solutions, and organizational actions currently
exist or will become available in the next 20 years. Among the possibilities, with different
emphases on economic efficiency and equity, are the following
• Through better informed travelers, allocate scarce highway capacity to road users
based on their expected travel time and unreliability (e.g. likelihood of being late).
Historically, travel time has been regarded as the primary price road users pay on
free roads and which has been the basis for allocating scarce roadway capacity.
• Charge each road user the full costs for using the roadway network.
• Set up reservation systems and allow people to reserve space in the traffic stream at
a specific point in time.
These types of changes, solutions, and actions will allow more effective management of
transportation demand, increases in person and freight moving capacity, and faster recovery of the
capacity lost to various types of disruptions. A wide range of activities will be employed by groups
ranging from individual travelers, carriers, and shippers, to highway agencies, local governments,
and private companies that supply services that support roadway operations.
EXECUTIVE SUMMARY
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