Warning Lights and Warning Messages for Nighttime Maintenance Work Zones: How to Get Them “Just Right” Gerald Ullman, Ph.D., P.E. Senior Research Engineer Texas Transportation Institute Nighttime Maintenance Work Activities The good… ◦ ◦ ◦ ◦ Lower traffic volumes Less congestion and delay Reduced driver rage Cooler temperatures The bad… ◦ ◦ ◦ ◦ Higher speeds Increased levels of impaired driving Worker fatigue Higher intrusion risk? Goals When Working at Night Gain motorist attention Provide sufficient and positive guidance information (minimize confusion) Flashing vehicle warning lights and temporary traffic control devices need to do both Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern I T Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern I T Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern I T Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern Color Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern Color Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern Color Location on vehicle Key Considerations of Vehicle Warning Lights Type (halogen, strobe, LED) ◦ Flash intensity ◦ Flash structure ◦ Flash pattern Color Location on vehicle Number in overall visual field Consequences of Excessive Vehicle Warning Lights Glare Masking effects Consequences of Excessive Vehicle Warning Lights Glare Masking effects “Moth” effects Consequences of Excessive Vehicle Warning Lights Glare Masking effects Consequences of Excessive Vehicle Warning Lights Glare Masking effects “Moth” effects Consequences of Excessive Vehicle Warning Lights Glare Masking effects “Moth” effects Photosensitive epilepsy concerns ◦ Critical range: 5-10 Hz ◦ Effects of multiple flashing light sources unknown Current Recommendations (NCHRP 624) Outline the vehicle Total luminance output of all visible lights limited to 2200 cd at night Flashing lights preferred over steady lights Slower flashes preferable Consider the entire convoy Warning Messages on TruckMounted Changeable Message Signs TMCMS use increasing for mobile and short duration operation ◦ Good detection ◦ Message flexibility Smaller size makes message design more challenging Mobile Operation Concerns Speed Differential Passing Wet Paint Workers Out of Vehicles Visibility Basic Message Design Principles No more than 4 units of information Each unit of information should be readable for two seconds No more than two phases Each phase should stand alone Acceptable TMCMS Phrases [#] PAINT TRUCKS [#] WORK TRUCKS SWEEPING AHEAD YELLOW [WHITE] LINE WET CNTRLINE WET DO NOT CUT IN WATCH FOR WORKERS REDUCED VISION STAY IN LFT [RGT] LANE Questions? Gerald Ullman Texas- Transportation Institute (979) 845-9908 3135 TAMU College Station, TX 77843-3135 [email protected]
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