Three prototype automatic ramp rollover warning systems were deployed around the Washington, DC metropolitan area. The systems were designed and installed at three curved exit ramps on the Capital Beltway in Virginia and Maryland:

• • I-495W/I-95S in Springfield, Virginia
  • I-495W/Route 123N in McLean, Virginia
  • I-495E/I-95N in Beltsville, Maryland

A typical installation included the following components for a one-lane ramp:

• • 2 weigh-in-motion (WIM) stations (loop-piezoelectric-piezoelectric configurations) for measuring vehicle weight, vehicle classification, and vehicle speed (installed 100 feet apart).
  • 1 controller unit located near the second WIM sensor station.
  • 1 height detector located near the second WIM sensor station.
  • 1 fiber optic warning message sign mounted below a static warning sign and 200 feet from WIM station 2.
  • 1 weigh-in-motion (WIM) sensor located beyond the fiber optic sign for measuring vehicle speed for evaluation purposes.

For a two-lane ramp, the components per lane would be the same as listed above.

The system used data from WIM and height detectors to determine if a truck would exceed its rollover threshold (RT) critical speed at the point of curvature. If the software determined that the maximum safe speed would be exceeded, then a fiber optic message sign would be activated. The message would read “TRUCKS REDUCE SPEED.”

The cost of this system included 1) software modification, 2) construction, and 3) system calibration, commissioning, testing, and design. The total costs were $166,462 for a one-lane ramp and $268,507 for a two-lane ramp. These costs are for a prototype rollover warning system. According to the report, by using fewer WIM detection sensors, eliminating certain items (e.g., the rollover algorithm, height detector) and using other detection technologies (acoustic sensors) the cost of future versions of the system could be lower.