5.0 Toll Collection Equipment Technology

5.6.4 Recommended Guidelines

VES Design Issues

• For VES cameras installed on a stanchion and mounted to the toll island or the top of a barrier, adequate horizontal clearance from the vertical face of the toll island curb or travelway, respectively, must be provided to avoid damage from passing vehicles.
• For supplemental lighting that is not an integral part of the camera assembly and is installed on a stanchion and mounted to the toll island or the top of a barrier, adequate horizontal clearance from the vertical face of the toll island curb or travelway, respectively, must be provided to avoid damage from passing vehicles.
• Mounting the camera on the toll island or to the top of a concrete barrier where visibility to passing motorists is high, the incidence of unsafe evasive moves by violators to avoid detection is expected to be higher.
• Supplemental lighting mounted at the approach and departure end of the toll island for rear and front license plate image capture, respectively, must not blind or impair the vision of the motorist when passing through a toll lane.
• Supplemental lighting mounted overhead at the approach and departure ends of the toll island below must not blind or impair the vision of the motorist when passing through the toll lane.

VES Guideline Development:

• To limit the number of camera lenses deployed and stored as spares to an absolute minimum,a toll island mounting location and associated image capture trigger distance that applies to all plaza lanes for both approach and departure cameras must be found. Since it is common foralternate toll islands to have canopy column supports and tunnel stairwells and for tollboothsto be protected by ramparts and concrete structures (e.g., crash blocks, planters), finding a common image capture trigger distance can be problematic. Once a common distance is found, a camera mounting angle within the vendor specified range of image capture anglesmust be selected that results in a high success rate of license plate optical character recognition. This angle effectively determines the camera mounting location on the toll island.Using the same guideline development logic that was used for the island traffic signal, a minimum horizontal clearance of 12 inches from the vertical face of the toll island curb should be maintained.
• When concrete barrier is installed along the lane, the camera can either be installed on astanchion mounted behind the barrier or mounted to the top or the barrier if it is a minimum of 12 inches from the travelway. Increasing the horizontal clearance may be warranted toaccommodate an agency’s roadway maintenance operations and vehicles.
• Vendor solutions for assuring toll facility users are not blinded or have their vision impaired by supplemental lighting used to improve the quality of captured license plate images varyfrom triggered pulsed/flashed or strobe lighting, infrared lighting (continuous and triggered),continuous white lighting with filters and diffusers/baffles, and continuous concentrated white directional lighting. Pulsed or flashed lighting usually involves high intensity LEDsproducing white lighting that is best suited to handling multiple colored license platecharacters and backgrounds corresponding to different jurisdictions. The millisecond flashesfor pulsed and strobe lighting that are only triggered when a violation is detected are intendedto be unnoticeable by the user. Supplemental lighting is always installed either adjacent to a camera or combined with a camera into a single unit of equipment. For cameras mounted toa stanchion and installed on a toll island, the lighting is either mounted to the same stanchionor separately on another stanchion. All of the lighting alternatives listed above can be used for both front and rear license plate image capture when deployed on a toll island or barrier. Forcameras mounted overhead, continuous white lighting, even with the use of filters anddiffusers, is likely to cause visual impairment to the user when passing through a toll lane. Triggered lighting using a reliable and accurate trigger should assure the light is not energizedwhen a vehicle’s windshield and light rays from the installed supplemental lighting intersect. While the user is far less susceptible to vision impairment from rear license plate overhead lighting (i.e., continuous white lighting), empirically supported by anumber of agencies that have deployed and are still using continuous white lighting for rear capture, front license plate lighting must dictate the type of lighting used system-wide. Using the same light source assures the following: 1) consistency in the quality of all images captured and processed by aviolation processing system; 2) less spares and corresponding storage space; and 3) less time needed to repair or replace due to technician familiarity. If only rear license plate imagecapture is to be deployed, continuous lighting should only be considered if the VES suppliercan demonstrate superior image quality and consistency using continuous white lighting.Otherwise the disadvantages of continuous lighting, namely user vision impairment whenusing the rear view mirror, and incurring significantly higher utility and lamp replacementcosts, are expected to exceed the identified benefits. From a safety and operationalperspective, it is recommended continuous white lighting of front license plates not be deployed when mounted overhead.

VES Design Guidelines

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