Roadway Safety Tools for Local Agencies (2003)

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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. Slippery surface 3. Large turning volume 4. Inadequate roadway lighting 5. Excessive speed on approaches 6. Lack of adequate gaps for turning vehicles 7. Absence of turning lanes 8. Crossing pedestrians 9. Uncontrolled access at intersection 10. Short turning radius 11. Inadequate directional signing Rear-end collisions at signalized intersections 1. Slippery surface 2. Large turning volume 3. Poor visibility of signals 4. Inadequate signal timing 5. Unwarranted signal 6. Inadequate roadway lighting 7. Excessive speed on approaches 8. Crossing pedestrians 9. Uncontrolled access at intersection 10. Short turning radius 11. Inadequate directional signing Right-angle collisions at unsignalized intersections 1. Restricted sight distance 2. Large total intersection volume 3. Excessive speed on approaches 4. Inadequate roadway lighting 5. Inadequate advance warning of intersection 6. Inadequate traffic control devices Right-angle collisions at signalized intersections 1. Restricted sight distance 2. Excessive speed on approaches 3. Poor visibility of signals 4. Inadequate signal timing 5. Inadequate roadway lighting 6. Inadequate advance warning of intersection 7. Large total intersection volume Left-turn head-on collisions at intersections 1. Large volume of left turns 2. Restricted sight distance 3. Short amber phase 4. Absence of special left-turning phase 5. Absence of left-turn lane 6. Excessive speed on approach Sideswipe collisions at intersections 1. Inadequate pavement markings 2. Inadequate roadway design (narrow lanes, restrictive alignment, etc.) 3. Short turning radius 4. Uncontrolled access at intersection 5. Parking too close to intersection 6. Inadequate directional signing Continued on next page

126 ABNORMAL CRASH PATTERNS & POSSIBLE CAUSES (continued) ABNORMAL CRASH PATTERNS POSSIBLE CAUSES Section 1: Intersections (continued) Pedestrian–vehicle collisions at intersections 1. Restricted sight distance 2. Inadequate pedestrian signs, signals, or markings 3. Inadequate signals 4. Improper signal phasing 5. Inadequate warning to drivers of frequent pedestrian crossings 6. Inadequate pavement markings 7. Inadequate gaps at unsignalized intersections 8. Inadequate roadway lighting 9. Excessive vehicle speeds Section 2: Environmental conditions Wet-pavement collisions 1. Slippery surface 2. Inadequate drainage 3. Inadequate delineation 4. Excessive vehicle speeds 5. Irregular pavement surface Nighttime collisions 1. Poor visibility or lighting 2. Poor sign quality 3. Inadequate channelization or delineation 4. Excessive vehicle speeds 5. Variable lighting conditions Reduced-visibility collisions 1. Inadequate warning of dense fog or smoke conditions 2. Inadequate delineation for conditions 3. Inadequate route guidance 4. Highly variable visibility conditions 5. Large vehicle speed variations 6. Excessive vehicle speeds Source: Traffic Safety Toolbox: A Primer on Traffic Safety (9), Table 25-2. BASIC FIELD OBSERVATIONS USED TO STUDY PROBLEM LOCATION Physical Inventory Parameters Operational Problem Symptoms (supplement construction plans) • Length of vehicle queues • Sight distance restrictions • Erratic vehicle maneuvers such as • Pavement and shoulder conditions – Stopping or backing at gore points • Signal visibility – Wrong-way movements • Signs, including speed limits – Gore area encroachments • Curb radii – Shoulder encroachments • Pavement markings – Traffic violations • Lighting • Vehicles experiencing difficulty in making turning movements • Driveway locations • Evidence of unreported accidents such as damaged guardrail or • Fixed objects and roadside design skid marks or tire tracks off of the pavement • Pedestrians on roadway • Pedestrian–vehicle conflicts Source: NCHRP Report 440: Accident Mitigation Guide for Congested Rural Two-Lane Highway (43), Table 10.

127 Source: Homburger et al., Fundamentals of Traffic Engineering (47), Figure 9-6.

128 Source: Homburger et al., Fundamentals of Traffic Engineering (47), Figure 9-7.

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) Prohibit left turns Provide adequate channelization Reroute left-turn traffic Provide traffic signal Add turn lane Install or improve warning sign Install STOP signs (see MUTCD) Install or improve pedestrian crosswalk Provide traffic signal Install STOP bars Provide left-turn signal Short Turning Radii for a Right Turn Increase left-turn bay length or taper length Increase curb radii Large Volume of Left Turns at Signalized Intersection Prohibit right turn on reds Prohibit left turns Add right-turn indication to signal Reroute left-turn traffic Large Total Intersection Volume Add turn lane Install signals (see MUTCD) Provide left-turn signal Add lane Provide adequate channelization Retime signal if signal is present Revise signal timing (length, phase sequence, etc.) Inadequate Roadway Lighting Provide turning guidelines (if there is a dual left-turn lane) Improve or add roadway lighting Increase left-turn bay length or taper length Advance Intersection Warning Signs Amber Phase Too Short at Signalized Intersection Install or improve warning signs Adjust amber phase Install hazard beacons Provide all-red phase High Approach Speed Increase amber phase if signal is located after a downgrade Reduce speed limit if justified by a study and there is a high percentage of trucks Install rumble strips Absence of Left-Turn Phase at Signalized Intersection Adjust amber phase Provide left-turn signal phase Signal Timing Prohibit turns Adjust amber phase Split phase Provide all-red clearance phases Add multi-dial controller Install signal actuation Retime signals Provide progression through a set of signalized intersections Continued on next page

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) Add multi-dial controller Provide pedestrian “WALK” phase if signal is present Install signal actuation Driver Not Aware of Intersection Retime signals Install/improve warning signs Provide protective movement phases Reduce speed limit if justified by a study Restricted Sight Distance Install hazard beacons Provide adequate channelization Large Numbers of Turning Vehicles Remove sight obstruction Create left- or right-turn lanes Install or improve warning sign Prohibit turns Install hazard beacons Increase curb radii Prohibit parking Provide left-turn signal phase if signal is present Provide markings to supplement signs Inadequate Roadway Lighting Improve roadway lighting Poor Visibility of Signals Install/improve advance warning devices Install 12-in. signal lenses (see MUTCD) Install visors Install back plates Improve location of signal heads Add additional signal heads Reduce speed limit if justified by a study Remove sight obstruction Install overhead signal Relocate signal Increase amber phase Slippery Surface Overlay pavement Provide adequate drainage Groove pavement Reduce speed limit if justified by a study Provide “Slippery When Wet” signs Improve roadway lighting Excessive Speed Reduce speed limit if justified by a study Inadequate Signal Timing Adjust amber phase Provide progression through a set of signalized intersections Provide all-red phase Unwarranted Signals Remove signals (see MUTCD) Source: NCHRP Report 440: Accident Mitigation Guide for Congested Rural Two-Lane Highway (43), Table 14.

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? ___ ___ 3.Do drivers have trouble finding the correct path through the locations? ___ ___ 4.Are vehicle speeds too high? Too low? ___ ___ 5.Are there violations of parking or other traffic regulations? ___ ___ 6.Are drivers confused about routes, street names, or other guidance information? ___ ___ 7.Can vehicle delay be reduced? ___ ___ 8.Are there traffic flow deficiencies or traffic conflict patterns associated with turning movements? ___ ___ 9.Would one-way operation make the location safer? ___ ___ 10.Is this volume of traffic causing problems? ___ ___ 11.Do pedestrian movements through the location cause conflicts? ___ ___ 12.Are there other traffic flow deficiencies or traffic conflict patterns? ___ ___ PHYSICAL CHECKLIST: 1.Can sight obstructions be removed or lessened? ___ ___ 2.Are the street alignments or widths inadequate? ___ ___ 3.Are curb radii too small? ___ ___ 4.Should pedestrian crosswalks be relocated? Repainted? ___ ___ 5.Are signs inadequate as to usefulness, message, size, conformity, and placement? (See MUTCD) ___ ___ 6.Are signals inadequate as to placement, conformity, number of signal heads, or timing? (See MUTCD) ___ ___ 7.Are pavement markings inadequate as to their clearness or location? ___ ___ 8.Is channelization (islands or paint markings) inadequate for reducing conflict areas, separating traffic flows, and defining movements? ___ ___ 9.Does the legal parking layout affect sight distance, through or turning vehicle paths, or traffic flow? ___ ___ 10.Do speed limits appear to be unsafe or unreasonable? ___ ___ 11.Is the number of lanes insufficient? ___ ___ 12.Is street lighting inadequate? ___ ___ 13.Are driveways inadequately designed or located? ___ ___ 14.Does the pavement condition (potholes, washboard, or slick surface) contribute to accidents? ___ ___ Comments: __________________________________________________________________________________________________ __________________________________________________________________________________________________ __________________________________________________________________________________________________ Source: NCHRP Report 440: Accident Mitigation Guide for Congested Rural Two-Lane Highway (43), Figure 3.

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

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) Regulate minimum corner clearance High Speeds at Intersections Move driveway to side street Install intersection ahead warning signs Install curb to define driveway location Install signal ahead warning signs Consolidate adjacent driveways Install rumble strips on intersection approach Large Volume of Main Street Traffic Move driveway to side street WET PAVEMENT Construct a local service road Slippery Pavement Reroute through traffic Overlay with skid resistant surface Add traffic signal (see MUTCD) Provide adequate drainage Right-Turning Vehicles Groove existing pavement Provide right-turn lanes Reduce speed limit if justified by a study Restrict parking near driveways Provide “Slippery When Wet” signs Increase the width of the driveway Inadequate or Improper Pavement Markings Widen through lanes Improve or install pavement markings Increase curb radii Prohibit turn BICYCLE ACCIDENTS Add acceleration lane Inadequate or Improper Pavement Markings Large Volume of Driveway Traffic Improve or install pavement markings Provide traffic signal Provide signs to supplement markings Provide acceleration and deceleration lanes Inadequate Roadway Lighting Provide adequate channelization Improve roadway lighting Restricted Sight Distance Remove sight obstructions Restrict parking near driveway Install/improve street lighting Reduce speed limit if justified by a study Install hazard beacons Excessive Speed Reduce speed limit if justified by a study Inadequate Roadway Lighting Improve roadway lighting Regulate minimum driveway spacing Continued on next page

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), Table 13.

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.

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) Install acceleration or deceleration lane Improve roadway lighting Repair road surface Provide traffic signal (see MUTCD) Inadequate Signing/Marking Install illuminated street name sign RIGHT TURNS Install advance guide sign High Approach Speed Improve or install pavement markings Reduce speed limit if justified by a study Install rumble strips HEAD-ON ACCIDENTS Roadway Design Roadway Design Increase curb radii Widen lanes Install acceleration or deceleration lane Provide turn bays Install/improve pavement lane lines REAR END Remove parking Driver Not Aware of Intersection Install median barrier/rumble strips Install/improve warning signs Reduce speed limit if justified by a study Large Numbers of Turning Vehicles Create left- or right-turn lanes Prohibit turns Increase curb radii Install acceleration or deceleration lane Excessive Speed Reduce speed limit if justified by a study Inadequate Roadway Lighting Improve roadway lighting Source: NCHRP Report 440: Accident Mitigation Guide for Congested Rural Two-Lane Highway (43), Table 12.

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. Install guardrail or crash cushioning device Reduce number of utility poles Roadway Design Increase recovery distance Flatten sideslopes Install rumble strips Provide proper superelevation Widen lanes Repair road surface Reshape ditch Convert ditch to a closed drainage system Design drainage facility flush with roadside terrain Install or improve warning signs Shoulder Drop-off Upgrade shoulder Repair shoulder Slippery Pavement Overlay existing pavement/improve skid resistance Provide adequate drainage Groove existing pavement Reduce speed limit if justified by a study Provide “Slippery When Wet” signs Widen lane or shoulders Poor Delineation Improve/install pavement markings Install roadside delineators Install advance warning signs (e.g., curves) Install raised pavement markers Excessive Speed Reduce speed limit if justified by a study Inadequate Roadway Lighting Improve roadway lighting Poor Traffic Control Device Visibility Increase sign size Install reflectors on obstruction Use larger letters on sign Illuminate sign Use brighter grade material Add beacons on advanced warning signs Source: NCHRP Report 440: Accident Mitigation Guide for Congested Rural Two-Lane Highway (43), Table 13.