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Enhancing Highway Safety at Left-Side Exit Ramps

Explore factors affecting left-side exit ramp accidents on I-75, including design information, accident history, and needed improvements based on MUTCD compliance. Learn about post-accident changes and recommended improvements.

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Enhancing Highway Safety at Left-Side Exit Ramps

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  1. Highway Factors David Rayburn

  2. Summary of Highway Factors • General Highway Information • Highway Design • Accident History • Traffic Control Devices

  3. General Highway Information • Average traffic speed 70 mph • Design speed 60 mph • Posted speed limit 55 mph • Motorcoach traveling 65 mph • Average daily traffic • I-75 was 95,920 vehicles • HOV lane was 6,825 vehicles • HOV ramp was 500 vehicles

  4. I-75 Design Information • Reconstructed 1982 • Four lanes and full-time HOV lane in each direction • HOV lanes separated from general use lanes by double line pavement markings (solid and dashed) • HOV left-side exit ramps operated as conventional ramps until 1996

  5. Exit Ramp Characteristics • Left-side exit ramp • First left HOV exit along I-75 • Approaching the accident site, roadway curves to the left • Driver’s view obstructed • Exit ramp is short

  6. Exit Ramp Accident History • 9 accidents between 1997 and 2007 • 3 were fatal • 6 of 9 involved single vehicle • Of the 6 single-vehicle accidents, 5 occurred at night • None of the drivers were from the Atlanta area

  7. Conventional Left Exit

  8. I-75 HOV Lane Separation

  9. MUTCD Compliance Required • Traffic Control Devices (TCDs) must comply with the Manual on Uniform Traffic Control Devices • TCDs include signs, signals, and pavement markings • The MUTCD provides: Standards Guidance Options

  10. Guide Signs for the HOV Exit Exit 1 mile Exit ½ mile Exit arrow Exit gore sign

  11. Traffic Control Devices

  12. Traffic Control Devices

  13. Traffic Control Devices

  14. E Traffic Control Devices on Ramp

  15. Postaccident Changes

  16. Stop Sign Beacon Added

  17. Pavement Markings • Guide line markings across direct exits can help minimize errant departures • FHWA recommends white dashed pavement markings in taper area • “Exit” or “Exit Only” pavement marking can also be used on ramps

  18. Needed Improvements • Left EXIT plaques on guide signs and implement within 5 years • Left exit direction (arrow) sign paired with pull-through sign • Advisory speed limit signs on exits • Exit pavement markings • Uniform guidance in the MUTCD

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