Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Appendices
actuated speed limits are displayed by variable message signs. In the Netherlands, about half of the
freeway network is equipped with traffic control systems that display variable speed limits. In
Germany, variable speed limits are currently used on approximately 750 miles (1200 km) of
freeways (approximately 10% of the network), with further increases expected in the near future.
The difference between the application of variable speed-limit systems in Europe and the United
States is that European systems use ITS technologies to automate changes in the posted speed limit
according to traffic volume thresholds, whereas in the US, changes to the posted speed limit are
typically applied by time of day or manually. The European system facilitates a rapid response to
changes in traffic demand, which provides better traffic flow on the roadways (8, 17 and 18).
In the United States, variable speed limits are being used along several interstates such as the I-70
Eisenhower Tunnel in Denver, Colorado (advisory downgrade speeds for trucks), and the I-90,
Snoqualmie Pass in Washington (regulatory speed for all traffic based on weather conditions) (14).
A major challenge of variable speed limits is motorist compliance. Inappropriate signs and
arbitrary speed restrictions, particularly at low volumes, lead to reduced compliance (6).
5.6 Congestion Pricing
Congestion pricing, also known as value pricing, uses variable and area-wide tolls to reduce traffic
volume during particular times of congestion or in particular areas of congestion. The main goal of
congestion pricing (and metering) strategies is to manage demand rather than supply. These
strategies can significantly improve the operations of a roadway. Congestion or value pricing is the
practice of charging tolls for the use of a facility according to the severity of congestion on the
facility itself or on a parallel facility. The objective of congestion pricing is to preserve high
operating speeds by employing a tolling system that encourages drivers to switch to other times of
the day, other modes, or other facilities when demand is near facility capacity. The pricing scheme
can be static or varied according to daily demand. Many applications of various static congestion
pricing schemes already exist, including those in London and Singapore (6, 8, 17 and 18). In the
U.S. variable pricing schemes are currently applied along managed and express lanes (i.e., SR 91
in Orange Country and I-95 in South Florida).
Electronic Toll Collection. New tolling technologies can help reduce the complexity and improve
the accuracy of congestion pricing in addition to expediting the tolling process. Technology such
as electronic tolling helps reduce the delay associated with paying for tolls. The E-Z Pass system
in the northeast region of the United States and Autopass out of Norway electronically debit an
account as the user drives through a toll plaza.
Electronic toll collection eliminates the need for a vehicle to come to a complete or near stop in
order to pay the toll. Some systems are able to collect tolls at full freeway speeds while others that
are retrofitted to an existing manual toll collection facility require vehicles to slow to speeds of 25
mph or less for safety reasons. Electronic toll collection may use toll tag readers, license plate
recognition, cell phones, or GPS units.
Cordon Pricing (Area wide). Cordon pricing imposes tolls for vehicles entering a central area
street network during certain hours of certain days. Singapore, London, and Stockholm are
international examples of this congestion pricing method. The toll may be reduced or waived for
certain vehicle types such as those with high occupancy (6, 8, and 14).
Congestion pricing is a valuable tool that can prevent a roadway system from breaking down
during peak periods by sustaining good service rates. Beyond improving operations, congestion
ADDITIONAL DESCRIPTION AND QUANTITATIVE BENEFITS OF TRAVEL-TIME RELIABILITY STRATEGIES Page F-12