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A tunnel is defined as a structure over a roadway that restricts the normal daytime illumi­nation of a roadway section so that the driver’s visibility is substantially diminished. Design of tunnel lighting requires adaptation for driver needs in the approach, and the FIGURE 7.59 Lighting adaptation zones for tunnel lighting. Approach: The external roadway area […]

Recommended values for illuminance, luminance, and small-target visibility are pub­lished as Tables 2, 3, and 4 in ANSI/IESNA RP-8-00, American National Standard Practice for Roadway Lighting, www. iesna. org. These lighting criteria for the three recognized calculation methods are typically adopted by AASHTO and published as a part of the AASHTO Guideline for Roadway Lighting. […]

Fixed roadway lighting systems increase night visibility, as well as improve safety, traffic movement, and general roadway use. Traffic volume, numbers of pedestrians, at-grade intersections, turning movements, signalization, and unusual geometrics are some elements that make lighting of streets and highways desirable. Lighting, in addi­tion to its safety benefits, is a crime deterrent and a […]

Continuous, complete, or partial interchange lighting is considered to be justified in the following situations: • In general, lighting is warranted where the local government agency finds sufficient benefit in the forms of convenience, safety, policing, community promotion, public relations, etc., to pay an appreciable percentage of the cost of the installation, main­tenance, and operation […]

Complete lighting of freeway interchanges is warranted under the following circumstances: Case CIL-1. Where total current ADT ramp traffic entering and leaving the freeway within the interchange area exceeds 10,000 for urban conditions, 8000 for suburban conditions, or 5000 for rural conditions. Case CIL-2. Where current ADT on the crossroad exceeds 10,000 for urban con­ditions, […]

Freeway lighting can substantially reduce accident frequency and increase capacity. Lighting is of additional benefit in freeway operations by providing motorists addition­al warning time of stalled or disabled vehicles on the roadway. A listing of the specific conditions considered by most authorities to warrant lighting is included below. 7.16.1 Warranting Conditions for Continuous Freeway Lighting […]

The above classifications appropriately describe general conditions of vehicular traffic conflict in urban areas. A second type of conflict is vehicle/pedestrian interaction. The magnitude is mostly determined by the land use of the abutting properties. Three clas­sifications of pedestrian night activity levels and types of land use with which they are typically associated are used […]

The following descriptions of facility types and area classifications are used to describe the warranting conditions and design needs of roadway lighting. 7.15.1 Roadway, Pedestrian Walkway, and Bikeway Classifications [3, 6] • Freeway. A divided major roadway with full control of access (no crossings at grade). This definition applies to toll as well as nontoll […]

Available computer programs accurately design lighting systems using photometric curves and data for various fixtures. Some programs allow the user to input items such as trees and other physical barriers that may interfere with the output from the light fixtures. These programs will calculate luminance, illuminance, and glare. Dirt and maintenance factors that depend on […]

The potential traffic safety benefits of lighting are due to an increase in driver comfort and confidence resulting from enhanced vision. This reduces driving stress and tension, increases roadway capacity, and reduces the potential for traffic accidents. The eco­nomic return of roadway lighting is greatest in urban and suburban areas with high traffic volumes. Rural […]