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Highway Factors

Highway Factors. David Rayburn. Summary of Highway Factors. General Highway Information Highway Design Accident History Traffic Control Devices. General Highway Information. Average traffic speed 70 mph Design speed 60 mph Posted speed limit 55 mph Motorcoach traveling 65 mph

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Highway Factors

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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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