New traffic
monitoring system could reduce commute times, says UC Berkeley
researcher
17
Jan 2001
By
Catherine Zandonella, Media Relations
Berkeley
- Drivers who rely on radio traffic reports may soon have
an easier way to navigate the dreaded freeway commute.
A University
of California, Berkeley, professor and his team of students
have developed a way to get updates on traffic hotspots, alternative
routes and travel times - up to an hour in advance - via the
Internet or cellular phone.
The freeway
Performance Evaluation Monitoring System, or PeMS, will be
unveiled tomorrow (Thursday, Jan. 18) at the UC Berkeley-sponsored
Bay Area transportation town meeting. Developed by Pravin
Varaiya,
UC Berkeley professor of computer science and electrical engineering,
PeMS converts freeway monitoring data into real-time traffic
updates accessible via a Web portal. Varaiya is one of the
main researchers in the proposed UC Berkeley-led Center for
Information Technology Research in the Interest of Society
(CITRIS). A joint program with UC Santa Cruz and UC Merced,
CITRIS is a research initiative dedicated to creating technology
to improve everyday living.
Currently
PeMS is only available to engineers at the California Department
of Transportation (Caltrans) and to the research community.
But Varaiya hopes his invention will soon enjoy widespread
use through Internet service providers and public agency traveler
information efforts.
At the
heart of Varaiya's invention is software that converts data
from Caltrans' existing vehicle detection network into easy-to-read
tables and graphs. The PeMS Web page provides a map of the
entire freeway system in a given urban area. A color-coded
link provides the freeway speed, and an animation shows how
congestion starts and spreads. By selecting an origin and
destination on the map, the user can see how long each route
to the destination will take. PeMS also analyses traffic patterns
and predicts travel times up to an hour in advance.
While PeMS
has obvious advantages for commuters, Varaiya, who is UC Berkeley's
Nortel Networks Distinguished Professor, originally designed
the system to help Caltrans officials monitor traffic patterns.
"PeMS can be used by managers to get an overall view of traffic
trends, by engineers to spot and eliminate bottlenecks and
help them design solutions, by planners to evaluate proposals
for new routes," Varaiya said.
Caltrans
officials have already begun using PeMS. "The real benefit
of PeMS is it gives us a better understanding of what is happening
on the freeways," said John Wolf, chief of the Office of System
Management Planning in the Caltrans Traffic Operations Program.
According
to Varaiya's calculations, appropriate traffic management
in the Los Angeles area could save more than $1 billion per
year in lost time and fuel costs. And this estimate did not
include costs associated with pollution, increased accidents
or stress.
Using PeMS,
Varaiya found that the most efficient way to reduce commute
times is to keep freeway traffic moving at 60 miles per hour.
The best way to maintain this speed during peak use hours,
he said, is to limit the number of cars allowed onto the freeway.
This could mean longer waits at on-ramps, but, overall, the
trip time would be shortened.
Varaiya
envisions a system where drivers could be notified of the
best time to leave for the journey. "Instead of being parked
on the freeway, you could spend ten more minutes on your coffee
break or in your office," he said.
In addition
to its use in traffic management, PeMS can predict travel
times. For example, a 40-mile trip across Los Angeles on Interstate-10
can take from 40 to 130 minutes, depending on traffic. By
accessing PeMS, a traveler could inform business clients of
her arrival time.
Although
the software for each urban area must be customized, a new
Caltrans district can be added within weeks. Varaiya and his
students are currently adapting software for Los Angeles,
which generates one gigabyte (one billion bytes) of data per
day. The entire state generates an average of two gigabytes
per day.
PeMS is
not yet applicable in the Bay Area, where traffic has worsened
dramatically in the past five years, said Varaiya. But Caltrans
has recently increased availability of data from the detectors
at least 10-fold, said Judy Chen, chief of the Caltrans Office
of Traffic Systems.
Caltrans
also feeds data to TravInfo, a traffic information system
- dial 817-1717 in the nine-county Bay Area - maintained by
the Metropolitan Transportation Commission. But PeMS provides
more detailed analyses that can be used for research.
Each vehicle-counting
device, or loop detector, consists of an electrical wire buried
in the pavement. When a vehicle passes over the wire, the
metal in the vehicle causes fluctuations in the electric current.
A detector that monitors a four-lane highway can cost $100,000
or more.
For PeMS,
the loop detectors send data every 30 seconds to a Sun 450
computer workstation in the basement of UC Berkeley's Cory
Hall. PeMS software combines the 30-second readings into 5-minute
readings that yield the number of cars and their average speed
for each lane, and then combines the lane-by-lane data into
an overall measure of freeway flow, occupancy and speed.
Traffic
monitoring systems like PeMS can accommodate future demand
for the next five years, Varaiya said. However, long-term
solutions will require automated vehicle guidance systems
like those being developed by California Partners for Advanced
Transit and Highways (PATH), a collaborative public and private
effort to apply advanced technology to reducing traffic congestion,
air pollution and energy consumption.
Meanwhile,
Varaiya is working with computer science professor Jitendra
Malik to add video monitoring to PeMS. This project involves
placing video monitors atop buildings to track vehicle speed
and direction. Eventually, through CITRIS, the proposed UC
Berkeley center, Varaiya and Malik plan to expand their traffic
monitoring research to deploy tiny wireless sensors that can
beam traffic data to a central computing facility, yielding
even more precise estimations of traffic flow.
PeMS is
supported by Caltrans and the National Science Foundation
through California PATH.
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