摘要: |
Toll facilities (roads, bridges and tunnels) are used primarily for revenue generation to repay for
long-term debt issued to finance construction, capacity expansion, operations and maintenance
of these facilities. Tolls are one form of a broad concept known as road pricing. In addition to
revenue generation, road pricing is used for other reasons including transportation demand
management to reduce peak hour travel and the recurring traffic congestion on some corridors.
Tolling technologies have evolved rapidly in the past two decades and today offer many solutions
for toll collection. Traditional (mostly cash) tolling has been gradually replaced by electronic toll
collection (ETC) that enables users to go through toll lanes without stopping. In addition to
improving traffic safety and enhancing the efficient use of the existing infrastructure, ETC results
in reduction in toll collection costs.
The three most important components of ETC are user account identification, vehicle
classification (where vehicles are charged differently according to class), and determination of the
distance traveled. Most of the tolling agencies in Region-6 (and most of the U.S.) determine the
user fee based on the number of axles. The latter is often identified using induction loop sensors
buried in the pavement and energized by low-voltage electrical currents that produce
electromagnetic fields above the roadway. Vehicles traveling through these fields produce digital
signatures that are used to identify the number of axles. The loop sensors used by many tolling
authorities in the U.S. are manufactured by TransCore, Inc. and are known as “Intelligent Vehicle
Identification System (IVIS).
The IVIS sensors have high accuracy rate in classifying vehicles. However, loop detectors
present several problems including the intrusive nature of their installation and maintenance
(disruptive lane closures), high failure rate, sensitivity to rebar in concrete pavements, and their
undermining of the structural health of the surrounding pavement. Loop failure can result
because of several reasons including cracks across saw cuts, broken loop or lead-in wires, and
sealant failure.
The aim of this study is to provide tolling authorities in Region-6 with detailed analysis of the
fitness of various non-pavement-intrusive vehicle classification technologies (imaging, radar,
Lidar, thermal profiling, etc.) under different roadway, traffic, and environmental conditions to
inform decision-makers of the accuracy, performance, and lifecycle-cost of these technologies.
Toll facilities have multiple lane configurations including highways with multiple lanes at highway
speeds and ramps at reduced speed. The classification technology must be accurate at high
speed, low speed, single lane facilities, multiple lane facilities, and all kinds of weather. The
study involves in-depth review of available non-pavement-intrusive vehicle classification
technologies; gathering and analyzing data on the performance and cost of available
technologies from manufacturers and toll facility operators; and making presentations to the
tolling industry in Region-6. |