Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Appendices
arrival prediction, and adjustment of the downstream signal operation based on that prediction.
Traffic adaptive signal control systems coordinate the control of traffic signals along arterial
corridors, and adjust the signal phase lengths based on prevailing traffic conditions. Adaptive
signal control systems use algorithms that perform real-time optimization of traffic signals based
on current traffic conditions, demand, and system capacity. Detection systems in the roadway or
overhead inform the controllers of actual traffic that allows the signals to adapt to prevailing
conditions. Traffic adaptive signal control can improve traffic flow under recurring congestion as
well as traffic conditions caused by incidents and special events.
A few systems that are familiar to most traffic engineers include SCOOT developed in the UK
(used in Los Angeles), SCATS, developed in Australia, and OPAC and Rhodes (used in Tucson,
AZ and Seattle, WA) developed in the United States (6, 9, and 14).
Advanced Transportation Automation Systems. Research is currently underway to develop
systems that could automate all or part of the driving task for private automobiles, public
transportation vehicles, commercial vehicles and maintenance vehicles. This will likely be
achieved through cooperation with an intelligent infrastructure, which may include instrumented
roadways or dedicated lanes, or other infrastructure created by a public or private information
provider. The primary objective would be to safely increase the capacity and flow of existing
infrastructure. Infrastructure-vehicle automation will include applications such as:
• Automated transit systems in dedicated rights-of-way to increase the operational
efficiency of transit.
• Automated precision docking of public transportation vehicles to improve service to
transit users, particularly the disabled, the young, and the elderly.
• Dedicated lanes for automated trucks in urban or intercity corridors to improve goods
movement.
• Automated guidance of snow removal vehicles to increase the efficiency of winter
maintenance operations.
• Automated on-board monitoring and inspection systems for safety, weight, and cargo
clearance of commercial vehicles.
Smart Freight. A number of different technology-based systems will improve the efficiency of
freight flows as follows:
• Due to inspection requirements for safety, weight, permits, and entry documents, trucks
are required to stop at ports of entry, weigh stations, and borders. The use of weigh-inmotion
technology, combined with electronic seals to secure cargo, and biometric
driver identification can facilitate truck movements though these gateways.
• Unobtrusive inspection technologies, such as gamma ray machines, can also be used to
reduce the length and impact of the inspection processes at gateways.
• The use of freight brokerages and the development of load-matching software can
reduce the number of empty truck trips and reduce congestion.
• Research is underway in Europe to tag freight and use that information with control
models to automatically route freight so the goods find the most efficient way through
the transportation network.
• Because drivers have a limited number of hours of service before they are legally
required to stop, timely truck parking is an ongoing issue. Trucks that park on ramps
and along roads are a safety concern and contribute to congestion. Programs that
ADDITIONAL DESCRIPTION AND QUANTITATIVE BENEFITS OF TRAVEL-TIME RELIABILITY STRATEGIES Page F-10