Roadway Safety Tools for Local Agencies (2003) / Chapter Skim
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Pages 125-138
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From page 125... ...
125 APPENDIX H Reactive Crash Analysis Tables ABNORMAL CRASH PATTERNS & POSSIBLE CAUSES ABNORMAL CRASH PATTERNS POSSIBLE CAUSES Section 1: Intersections Rear-end collisions at unsignalized intersections 1. Drivers unaware of intersection 2.
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From page 126... ...
126 ABNORMAL CRASH PATTERNS & POSSIBLE CAUSES (continued) ABNORMAL CRASH PATTERNS POSSIBLE CAUSES Section 1: Intersections (continued)
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127 Source: Homburger et al., Fundamentals of Traffic Engineering (47) , Figure 9-6.
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128 Source: Homburger et al., Fundamentals of Traffic Engineering (47) , Figure 9-7.
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129 POTENTIAL COUNTERMEASURES FOR INTERSECTION ACCIDENTS TYPE OF INTERSECTION ACCIDENT Contributing Factor Potential Countermeasure LEFT TURNS RIGHT TURNS Restricted Sight Distance Restricted Sight Distance Remove sight obstruction Remove sight obstructions Provide turn lane Restrict parking near corners Prohibit left turns Install STOP signs (see MUTCD) Install or improve warning signs Install/improve street lighting Reduce speed limit if justified by a study Reduce speed limit if justified by a study Large Volume of Left Turns at Unsignalized Intersection Install YIELD signs (see MUTCD)
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From page 130... ...
130 POTENTIAL COUNTERMEASURES FOR INTERSECTION ACCIDENTS (continued) TYPE OF INTERSECTION ACCIDENT Contributing Factor Potential Countermeasure REAR END RIGHT ANGLE Pedestrian Crossing Inadequate Signal Timing Install/improve signing or marking of pedestrian crosswalks Adjust amber phase Relocate crosswalk Provide all-red clearance phases Install traffic signal (see MUTCD)
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From page 131... ...
131 ON-SITE OBSERVATION REPORT Location _________________________________________ Control ____________ Date ____________________________________________ Time ______________ OPERATIONAL CHECKLIST: NO YES 1.Do obstructions block the drivers' view of opposing vehicles? ___ ___ 2.Do drivers respond incorrectly to signals, signs, or other traffic control devices?
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From page 132... ...
132 POTENTIAL COUNTERMEASURES FOR OTHER ACCIDENTS TYPE OF OTHER ACCIDENT Contributing Factor Potential Countermeasure PEDESTRIAN ANIMAL Pedestrians Walking on Roadways High Number of Animal Accidents Install sidewalks Install advance warning sign Driver Has Inadequate Warning of Frequent Midblock Crossings Install fencing and underpasses to control animals crossing Prohibit parking the roadway Install or improve warning signs Install warning reflectors Reduce speed limit if justified by a study Encourage driver education about local animal behavior Install pedestrian barriers Excessive Speed NIGHT Install or improve warning signs Poor Traffic Control Device Visibility Reduce speed limit if justified by a study Install or improve warning sign Increase enforcement Improve roadway lighting Install pedestrian barrier Improve or install delineation Inadequate or Improper Pavement Markings Install hazard beacons Install thermoplastic markings Inadequate Delineation Provide signs to supplement markings Install or improve warning sign Improve or install pavement markings Improve or install delineation Inadequate Roadway Lighting Provide raised markings Improve roadway lighting Inadequate Channelization Lack of Adequate Gaps Install or improve warning sign Provide traffic signal Improve or install pavement markings Install or improve pedestrian crosswalk Improve or install delineation Provide pedestrian signal Provide raised markings Large Turning Volumes Inadequate Signing Create left- or right-turn lanes Upgrade traffic control devices Prohibit turns Provide illuminated sign Increase curb radii Provide pedestrian-only phase if signal is present Restricted Sight Distance Remove sight obstructions Install pedestrian crossings Improve/install pedestrian crossing signs Reroute pedestrian paths Restrict parking Inadequate Protection for Pedestrians Add pedestrian refuge islands Install pedestrian barrier to channelize pedestrian to a better crossing point Inadequate Signals Install pedestrian signals (see MUTCD) Inadequate Signal Phasing Add pedestrian "WALK" phase Change timing of pedestrian phase School Crossing Area Use school crossing guards Sidewalk Too Close to Traveled Way Move sidewalk laterally away from highway Continued on next page
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From page 133... ...
133 POTENTIAL COUNTERMEASURES FOR OTHER ACCIDENTS (continued) TYPE OF OTHER ACCIDENT Contributing Factor Potential Countermeasure DRIVEWAY/ACCESS ACCIDENTS EXCESSIVE SPEED Left-Turning Vehicles High Speeds Provide turn-lane barrier Increase conventional enforcement Install median Target specific locations or vehicle types Install two-way left-turn lanes Use speed radar trailers or speed display boards Prohibit turn Begin automated enforcement program Improperly Located Driveway Implement public relations campaign (perhaps using Regulate minimum spacing of driveways NHTSA materials)
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From page 134... ...
134 POTENTIAL COUNTERMEASURES FOR OTHER ACCIDENTS (continued) TYPE OF OTHER ACCIDENT Contributing Factor Potential Countermeasure WORK ZONE Narrow Work Zone Roadway Widen roadway by moving channelizing device or by using narrower devices Improve reflectivity and delineation of devices Illuminate or reflectorize channelizing devices Increase roadway width by routing traffic onto the shoulder Insufficient Advance Warning Move taper upstream to increase sight distance Add arrow board Drums Rolling into Travel Lane Replace drums with barricades Increase traffic control device inspection frequency Too Many Traffic Control Devices in or Near Roadway Provide portable concrete median barriers Increase spacing between devices Speeds Too High or High Variance in Speeds Increase design speeds Provide speed enforcement patrols Add advisory speed plates Add rumble strips Use variable message signs Large Vehicles Provide truck detours Widen work zone roadway Increase pavement strength Provide climbing lanes Insufficient Work Zone Traffic Capacity Provide alternative routes Change work schedule to exclude peak traffic periods Increase capacity by routing traffic onto shoulder Reduce length of work area Install warning area Poor Work Vehicle Access or Egress to Traffic Stream Change work vehicle access or egress points Provide flaggers Improper Flagging Technique Train flaggers Move flaggers upstream Replace flaggers with signal Provide extra flaggers positioned near the upstream end of vehicle queue Insufficient Taper Length Lengthen taper Add arrow board Position arrow board near start of taper Move taper upstream to increase sight distance Insufficient Acceleration Lane Length Lengthen taper Install YIELD or STOP sign on on-ramp Close on-ramp Build temporary ramp downstream Source: NCHRP Report 440: Accident Mitigation Guide for Congested Rural Two-Lane Highway (43)
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From page 135... ...
135 SUPPLEMENTARY ENGINEERING STUDIES Symptom of Operational Study Problem that Supplementary Study Purpose of Study Indicates Study Needed Capacity Studies To determine operating condition and - Congestion delays pinpoint bottlenecks Travel Time and To determine location and extent of delay - Intersection congestion Delay Studies and average travel speeds - Other congestion along roadway - Rear-end accidents during peak period Speed Studies To determine actual vehicle speeds, actual - Extremely high or low speeds observed during on-site visits speed profiles, and adequacy of legal and - Run-off-road accidents advisory speed limits - Rear-end accidents near intersections Traffic Conflict and To supplement traffic accident data and - Hazardous driver actions observed during on-site visits Erratic Maneuver identify potential accident problems - Public complaints of safety problems not evident in accident data Studies Traffic Signal Studies To determine need for and design of traffic - Right angle accidents at unsignalized intersections signals, to identify improper phasing, timing, - Excessive delay at STOP sign controlled intersections or interconnect strategy, and to identify - Excessive delay at existing signalized intersections unwarranted signals Sight Distance Studies To determine adequacy of the length of - Rear-end accidents at horizontal curves, crest vertical curves, highway visible to the driver or decision points - Right-angle accidents at uncontrolled intersections - Turning accidents at intersections Turning Radius Studies To determine adequacy of existing curb radii - Sideswipe accidents involving vehicles traveling in opposite directions - Rear-end accidents in right-turn lanes - Evidence of large vehicles encroachment on curb or shoulder Skid Resistance Studies To determine the coefficient of tire-pavement - Run-off-road or skidding accidents under wet-pavement conditions friction Source: NCHRP Report 440: Accident Mitigation Guide for Congested Rural Two-Lane Highway (43) , Table 11.
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From page 136... ...
136 POTENTIAL COUNTERMEASURES FOR ROADWAY ACCIDENTS TYPE OF ROADWAY ACCIDENT Contributing Factor Potential Countermeasure LEFT TURNS SIDESWIPE ACCIDENTS Large Volume of Left Turns (Including opposite- and same-direction sideswipe accidents) Add two-way left-turn lane Roadway Design Add turn bays at selected locations Widen lanes Restricted Sight Distance Provide turn bays Remove sight obstruction Install advanced route or street signs Install or improve warning signs Install/improve pavement lane lines Reduce speed limit if justified by a study Prohibit parking Provide turn lane Install median barrier Excessive Speed Install rumble strips Reduce speed limit if justified by a study Upgrade or widen roadway shoulder Lack of Adequate Gaps Provide turn lane Provide stop sign (see MUTCD)
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From page 137... ...
137 POTENTIAL COUNTERMEASURES FOR ROADSIDE ACCIDENTS TYPE OF ROADSIDE ACCIDENT Contributing Factor Potential Countermeasure RUN-OFF-ROAD ACCIDENTS (Including fixed-object, rollover, and other run-off-road accidents) Objects Near Traveled Way Remove obstacles Relocate obstacle away from roadway Install breakaway feature to light poles, signposts, etc.
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