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Open Access Publications from the University of California

Virtual Weigh Stations: The Business Case


Overweight trucks traveling illegally on the California highway network cause a significant and disproportionate amount of damage to pavements. Truck traffic is expected to account for some percentage of damage to pavements, however the percentage of pavement damage caused by overweight trucks is much greater than the expected damage from measured truck traffic volume on California highways. Many of these overweight trucks travel unmonitored throughout the network and cost the taxpayers millions of dollars every year in maintenance and rehabilitation costs.

Currently, Weigh and Compliance Stations run jointly by the California Department of Transportation (Caltrans) and the California Highway Patrol (CHP) are the sole instrument used to enforce weight and other restrictions on trucks. Currently, 38 weigh stations are strategically located throughout California. When a station is open, trucks not given a bypass signal must enter the scales and have each axle weighed. Trucks not in compliance are cited. The effectiveness of these weigh stations is limited by their operating hours, the routes they can monitor, and their operating and installation costs. Moreover, these stations can cause user delays from extended queue times for trucks waiting to be weighed.

Development of a new technology known as a Virtual Weigh Station (VWS) is currently underway. The VWS utilizes weigh-in-motion (WIM) sensors, located throughout the state, as tools for weight restriction enforcement. Caltrans Division of Traffic Operations traditionally has used these WIMs to provide data about traffic loads applied to California highway pavements. As a truck passes over a WIM, the type of truck, weight of individual axles, speed, and other data are recorded and stored by the WIM. Through the use of cameras, this data can be linked to the truck license plate and/or registration number. This data can then be relayed to the enforcing authorities, at which point trucks violating weight restrictions can be cited appropriately.

This memorandum was initiated by Caltrans for the Partners for Advanced Transit and Highways (PATH) in order to explore the idea of installing VWS in California. The study included a literature survey and expert interviews, as well as an analysis of estimated pavement performance benefits from VWS. The Pavement Research Center (PRC) was asked by PATH to estimate these benefits and other pertinent pavement information concerning overweight trucks. Specific objectives were the following:

* Estimate pavement damage caused by overweight trucks on the network. * Estimate costs of this pavement damage to Caltrans. * Estimate potential savings induced by the installation of VWS.

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