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Published byDerek Greene Modified over 9 years ago
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Access Management: South Carolina’s Experience Rick Werts Director of Traffic Engineering South Carolina Department of Transportation
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Presentation Outline What is access management? Resources SCDOT’s experience Current updates School access design Conclusions What is access management? Resources SCDOT’s experience Current updates School access design Conclusions
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What is Access Management? Access management is the systematic control of the location, spacing, design, and operation of driveways, median openings, interchanges, and street connections to a roadway. It also involves roadway design applications, such as median treatments and auxiliary lanes, and the appropriate spacing of traffic signals.
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www.accessmanagement.gov
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Resources
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Additional Resources Links to state DOT websites and manuals NCHRP research reports National conference information Past conference proceedings Outreach programs Training opportunities Links to state DOT websites and manuals NCHRP research reports National conference information Past conference proceedings Outreach programs Training opportunities
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TRB’s Access Management Manual
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Graphics Slide Background SCDOT’s Experience Increased growth in South Carolina Congestion has created a need for more specific access management guidelines Update current guidelines (1996) based on recommended practice from TRB’s Access Management Manual Increased growth in South Carolina Congestion has created a need for more specific access management guidelines Update current guidelines (1996) based on recommended practice from TRB’s Access Management Manual
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Driveway Classification Expected Trips Low Volume 1-20 trips/day 1-5 trips/hour Medium Volume 21-600 trips/day 6-60 trips/hour High Volume 601-4,000 trips/day 61-400 trips/hour Major Volume >4,000 trips/day >400 trips/hour Driveway design elements (width & radii) based on driveway classifications Driveway Design Elements Driveway ClassificationExpected Trips Low Volume 1-20 trips/day 1-5 trips/hour Medium Volume 21-600 trips/day 6-60 trips/hour High Volume 601-4,000 trips/day 61-400 trips/hour Major Volume >4,000 trips/day >400 trips/hour
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Driveway Design Elements Driveway ClassDriveway Width (feet) Minimum Radius Returns (feet) Low Volume10 – 24 15 Medium Volume24 – 36* 30 (40 Recommended) High Volume36** ** Major Volume** * A 36 ft. driveway is usually marked with two exit lanes of 11 ft. width, with the balance of 14 ft. used for a single, wide entry lane. A larger width will be required for a divided driveway design. **Driveway widths and lane requirements are determined by a traffic study.
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Throat Lengths Land UseDriveway Throat Length Major entrance to a development with 4 or more total lanes in the driveway >300 ft, based on traffic engineering study Regional Shopping Center (>150,000 sq. ft.) 250 ft. Community Shopping Center (100,000-150,000 sq. ft.) 150 ft. Small Strip Shopping Center50 ft. Commercial Developments (convenience stores, Gas Stations) 30 ft.
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Spacing based on speed limit and AADT Driveway Spacing Posted Speed Limit (mph) Minimum Driveway Spacing (ft) on roadways with AADT > 2000 Minimum Driveway Spacing (ft) on roadways with AADT < 2000 3016075 35220125 40275175 45325225 > 50400275
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Corner Clearances
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Interchange Areas Distance (ft) Description X 750 Distance from the closest interchange ramp to the first full access intersection Y 325 Distance from the off-ramp to the first right in, right out access point Z 325 Distance between the last right in, right out access connection and the on-ramp
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New School Sites Access Problems due to: Site Selection Inadequate internal storage Lack of turn lanes on roadway No traffic engineer in planning process Access Problems due to: Site Selection Inadequate internal storage Lack of turn lanes on roadway No traffic engineer in planning process
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New School Sites Planning Efforts undertaken: Met with State Education Department Expressed concern with site selection and school layouts Asked to be included in planning stages Planning Efforts undertaken: Met with State Education Department Expressed concern with site selection and school layouts Asked to be included in planning stages
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The Office of School Facilities Manual states: The SCDOT shall be consulted for roadway improvements whenever stacking loops or access to a school is modified, or whenever a new school is planned, or an addition that increase the number of students is planned. Access to a school site shall be defined by the SCDOT Traffic Engineering Division as part of the encroachment permit process. The Office of School Facilities Manual states: The SCDOT shall be consulted for roadway improvements whenever stacking loops or access to a school is modified, or whenever a new school is planned, or an addition that increase the number of students is planned. Access to a school site shall be defined by the SCDOT Traffic Engineering Division as part of the encroachment permit process. School Access Design
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Conduct an initial site review with School District representatives to identify potential access locations and roadway improvements Review detailed plans and provide any recommendations needed for final approval prior to issuing permit Conduct an initial site review with School District representatives to identify potential access locations and roadway improvements Review detailed plans and provide any recommendations needed for final approval prior to issuing permit School Access Design
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Guidelines for School Transportation Design
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On-Site Stacking Lengths requirements (900 ft-1,500 ft) Driveway Spacing requirements (600 ft. min) On-Site Stacking Lengths requirements (900 ft-1,500 ft) Driveway Spacing requirements (600 ft. min) School Access Design
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Driveway lane widths and corner radii School Access Design
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Results of Planning Efforts New schools open with minimal traffic problems No roads are blocked by stacking traffic New schools open with minimal traffic problems No roads are blocked by stacking traffic
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Conclusions Good planning yields good results Good access standards lead to less traffic congestion and lower vehicle crashes Good planning yields good results Good access standards lead to less traffic congestion and lower vehicle crashes
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