Perpetual motion

Jan. 29, 2018

Toward continuous, 24/7 traffic operations improvement

Facility operators can achieve continuous traffic operations improvement by optimizing traffic control in the predictable off-peak traffic period. But how?

First, evaluate continuous improvement opportunities. Are traffic-control devices subjecting traffic movements to unnecessary or extended stops under free-flow conditions? Are atypical conditions present in or adjacent to the roadway?

Areas susceptible to nighttime, adverse weather, and/or wildlife-crossing conditions magnify these conditions under high traffic speed and decreased driver attention. Vehicular conflicts through an intersection’s area of influence, where accelerating and decelerating occur, coupled with areas of encroaching roadside activities also detract from driver attentiveness.

Next, engage drivers toward active awareness and response to atypical road and traffic conditions. Electronic devices such as flashing beacons and message boards influence drivers who trust device communication on real-time conditions. Static devices like retroreflective sheeting on traffic-control sign posts boost driver attention to approaching road conditions.

In Mohave County, we are committed to continuous traffic operations improvement, and we fulfill that commitment by deploying an array of semi-passive and driver feedback solutions on high-speed rural roads.

The county installed an optical speed zone on a remote, two-lane highway that consisted of multiple speed bars, each representing a uniform transverse marking spaced variably in decreasing increments to convey to drivers a sensory perception of increased speed while their vehicle travels at or near constant speed through the zone, which targeted an instinctive driver reaction to relax the accelerator.

The county also established a speed-management zone using signs equipped with radar detection to activate solar-powered, sign-embedded LED lights when any approaching vehicle exceeded the posted speed limit. Installed on a rural, two-lane highway serving a high tourist traffic mix entering a business district, these speed feedback signs effected a 14% reduction in mean traffic speed.

Another safety improvement has been signage on a stop-controlled road entering a two-lane highway through a suburban area, which activates flashing beacons mounted around a LOOK FOR TRAFFIC warning sign when detecting an approaching vehicle, to give drivers time to take appropriate action. The county proved successful in responding to two separate occurrences of wrong-lane, head-on crashes involving drivers turning erroneously onto the leftmost road lane of a collector road accessing the Grand Canyon. Reinforced lane-use pavement markings complemented by two-way traffic-warning signs erected on each side of the road made this happen. (Five years on, no similar crashes of any severity have occurred in the area.)

Semi-passive and driver-feedback devices give flexibility toward systematic improvements addressing a broad range of conditions. Physical road improvements, such as centerline and edge-line rumble strips, give similar sensory advisory to drivers, so that they may take action and maintain control without succumbing to an impending hazard.

Operations-based improvements center on accurate, timely and corridor-coordinated traveler information dissemination across dynamic devices on instrumented road facilities.

Safety improvement intervention need not reinvent the wheel—only aid those in control
of it.

About The Author: Latoski is director of Mohave County Public Works in Arizona.

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