Transportation's Role in Reducing U.S. Greenhouse Gas Emissions ...

Transportation’s Role in Reducing U.S. Greenhouse Gas Emissions: Volume 2
both by improving efficiency (e.g., avoiding congestion) and reducing VMT. In some
cases, however, better information can have mixed effects. For example, if travelers take a
longer route to avoid an incident on their usual route, their VMT will increase, potentially
offsetting the GHG reduction from avoiding travel in congested conditions.
Traveler information can take a variety of forms:
• Road status information systems that provide information on roadway traffic
conditions and congestion, including travel times and major incidents or delays;
• Information on public transit, including real-time information on expected arrival
times, travel times, delays, etc., as well as systems to help people plan trips;
• Carpool information systems that provide advance or real-time information regarding
commuters or other travelers destined to the same area and willing to carpool;
• Multimodal information systems that provide travelers with information on the
various alternatives they have to get from point A to point B, considering different
modes of travel;
• Parking guidance and information systems that provide drivers with dynamic
information on parking within controlled areas and assist in searching for vacant
parking spaces; and
• Freight route management systems that help carriers make more efficient routing and
scheduling decisions in order to avoid congestion, reduce freight vehicle mileage, and
increase load factors (e.g., avoiding empty backhauls).
Traveler information is disseminated through a variety of mechanisms, including Internet
sites, 511 telephone information systems, auto texting and e-mails to mobile devices, invehicle
GPS equipment, television public service announcements, radio announcements,
public information kiosks, and dynamic (changeable) signs.
Highway traveler information has traditionally relied on the same information
infrastructure that supports intelligent traffic management through monitoring of traffic
conditions. Various levels of highway traveler information are present in most major U.S.
metropolitan areas. As of 2006, 63 of 100 surveyed metropolitan areas conducted realtime
traffic data collection on freeways, covering 38 percent of lane miles (Cambridge
Systematics, 2008). As of February 2008, 30 States had established 511 information
systems.
The private sector is taking a strong role in traveler information services. There is much
private sector activity underway to provide customized delivery of traveler information to
individual travelers via handheld and in-vehicle devices. Anonymous location tracking
using global positioning system (GPS)-enabled mobile phones is providing much more
comprehensive real-time information than older monitoring technologies such as loop
detectors, cameras, and probe vehicles. Private providers of real-time information such as
NavTeq/Traffic.com and Inrix cover many metropolitan areas – INRIX has real-time
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