Proposed ADHS “Super-2” Specifications

Proposed ADHS “Super-2” Specifications

· Minimum design speed of 65 mph (105 km/h) in rural areas, with 50 mph (80 km/h) allowed in mountainous and urban areas.

· Sight distance, curvature and superelevation according to the current edition of AASHTO's A Policy on Geometric Design of Highways and Streets for the design speed.

· Maximum grade determined by a table, with up to 6% allowed in mountainous areas and hilly urban areas.

· At least one lane in each direction, and more if necessary for an acceptable level of service in the design year, according to the current edition of AASHTO's A Policy on Geometric Design of Highways and Streets.

· Climbing lanes and emergency escape ramps should be provided where necessary for an acceptable level of service in the design year, according to the current edition of AASHTO's A Policy on Geometric Design of Highways and Streets.

· Minimum lane width of 12 ft (3.6 m).

· Minimum paved shoulder width of 10 ft (3.0 m)

· Pavement cross slope of at least 1.5% and preferably 2% to ensure proper drainage on straight sections. This can be increased to 2.5% in areas of heavy rainfall. Shoulder cross slope should be between 2% and 6% but not less than the main lanes.

· Roadside barriers should be used for slopes of 3:1 or steeper, in accordance with the current edition of AASHTO's Roadside Design Guide.

· No fixed objects should be in the clear recovery area, determined by the design speed in accordance with the current edition of AASHTO's Roadside Design Guide. When this is not possible, breakaway supports or barriers guarding the objects shall be used.

· Vertical curbs are prohibited. Sloping curbs are to be at the edge of the paved shoulder, with a maximum height of 100 mm (4 in). The combination of curbs and guardrail is discouraged; in this case the guardrail should be closer to the road than the curb.

· Minimum vertical clearance under overhead structures (including over the paved shoulders) of 16 ft (4.9 m) in rural areas and 14 ft (4.3 m) in urban areas, with allowances for extra layers of pavement. Through urban areas at least one routing should have 16 ft (4.9 m) clearances. Sign supports and pedestrian overpasses must be at least 17 ft (5.1 m) above the road, except on urban routes with lesser clearance, where they should be at least 1 ft (0.3 m) higher than other objects. Vertical clearance on through truss bridges is to be at least 17 ft (5.1 m).

· Super 2 roadways shall be constructed in such away that will allow for a second roadway to be constructed at a future date when traffic patterns dictate a divided highway is needed.

· Building set backs must be at least 100 ft (30.0 m) from the edge of the paved shoulder.

No more than one grade level crossing per 5000 ft (1500.0 m)