Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Appendices
and can have a positive impact on the reliability of trips for individual travelers. Travelers can take
a detour, change destination, or communicate their situation to others in the case of time-sensitive
commitments. The ability of traveler information to improve trip reliability will increase as
technology and avenues for transmitting traveler information improve traveler information.
Additional information about traveler information systems can be found in the NCHRP Synthesis
399 – Real Time Traveler Information Systems (13) report.
Pre-trip information by 511, real-time navigation systems, web sites, subscription alerts. Pretrip
information provides motorists data through the internet, television, or radio. Many Cities have
Advanced Traveler Information Systems (ATIS) with growing sophistication. These systems
incorporate close-to-real-time information from cameras and traffic reports and provide data via
the internet (14). Close-to-real-time information may have delivery delays of 30 minutes or more,
and this technology is still developing.
Many agencies also use phone systems and traffic hotlines such as 511 to collect and distribute
information about roadway conditions. Furthermore, many agencies’ websites (e.g., 511.org in San
Francisco and 511.ksdot.org in Kansas City) are starting to provide service to cell phones, which
allows people to also obtain information on the go (6).
Road Weather Information Systems. Road weather management systems reduce the disruptive
impacts of weather, using technology to promote safety, increase mobility, improve productivity,
and protect the environment. Adverse weather conditions pose a significant threat to the operation
of the Nation’s roads. Under extreme conditions (such as snowstorms), travel times can increase
significantly. Road Weather Information Systems (RWIS) are now critical components of many
agencies’ winter maintenance programs. Accurate and timely road weather information helps
maintenance managers react proactively before problems arise; thereby improving safety while
also reducing costs (9).
Freight Shipper Congestion Information. Freight Shipper Congestion Information refers to realtime
information along significant freight corridors. ITS technologies such as DMS, VMS, GPS,
and RFID are used to provide travel-time information to freight operators. As an example, these
technologies are evaluated by FHWA (6) along segments of I-5 (California, Oregon, and
Washington) and I-45 (Texas). It should be noted that the FHWA national corridor monitoring
data from transponders (via partnership with ATRI) are not available or used for real-time
monitoring. Many trucks are tracked via GPS, which is a great probe source. The challenge is to
gain access to this data (it is all private data) and use it to provide real-time information.
Weight-in-motion (WIM) technologies are another treatment to relieve congestion for freight
shippers. Even though WIM doesn’t provide real-time information to truck drivers, it does allow
agencies to reduce the freight screening time in weigh stations and, therefore, reduce truck queues
entering and leaving the stations. Additionally, data archived from WIM systems can be used to
estimate truck volumes at stations (and adjacent highways) and to better plan truck routes.
2.5. Roadside Messages
Roadside Messages (DMS). Roadside messages consist of dynamic message signs (DMS), also
known as variable message signs (VMS) that display information to travelers while they are
driving. DMS devices provide overhead or side-of-roadway warning, regulation, routing and
management information. These technologies are intended to affect the behavior of drivers by
providing real-time traffic information related to travel times, incidents, weather, construction, and
special events. DMS are ITS solutions that provide safety and mobility benefits in urban,
ADDITIONAL DESCRIPTION AND QUANTITATIVE BENEFITS OF TRAVEL-TIME RELIABILITY STRATEGIES Page F-4