21.2 Countermeasures for Mitigating Headlamp Glare

When a motorist encounters glare from other vehicles, they may experience discomfort or reduced visibility. Several design solutions are available to mitigate the effects of glare, and each carries its own advantages and disadvantages (Table 21.1). Designers should be mindful of project context when selecting countermeasures and pick those that will minimize negative side effects.

Table 21.1 Design Treatments to Mitigate Headlamp Glare
Treatment	Advantages	Disadvantages
Wide Medians	Reduce glare effect Greater object contrast due to lower background luminance	Higher construction and maintenance costs (e.g., more right of way required, median landscaping) Increasing the amount of time to cross an intersection can diminish the efficiency of traffic signal operations.
Independent Alignments	Can eliminate views of oncoming vehicles and associated glare Greater design flexibility due to less required earthwork on slopes and complex topography More environmentally friendly	Construction time is longer compared to facilities with narrow medians More right of way is required, which may increase cost and project duration.
Glare Screens	Reduce glare Installation can target problem areas Simple to install and maintain Cost-effective	A barrier must be present on which to install the screen Only effective if vehicles are on the same level plane Not a good option if significant vertical curvature is present
Fixed Road Lighting	Improves visibility of objects and pedestrians Increased adaptation level reduces glare effect	High installation, operation, and maintenance costs Fixed lighting poles may increase crash risk (breakaway mountains and larger setbacks can mitigate this risk)

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