Quantcast Geometric Design of Roadways

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7.3.1 Geometric Design of Roadways
The design of roadways in a Truck Inspection Facility will be in accordance with the guidelines
provided in Section 4.2.4 and the latest edition of the AASHTO Policy on Geometric Design of
Highways and Streets except as modified in this section. Additionally, the design should
consider the requirements to support oversized, atypical vehicles such as those frequently
encountered during construction operations.
7.3.1.1
Channelization Islands
The minimum raised channelization island will be 1524 mm (5 feet) in width, 160 mm (6
inches) in height and 15.2 meters (50 feet) long. A channelization island will be provided
between each incoming traffic lane. These islands provide a safe position for security
personnel and a location to mount present/future vehicle inspection devices.
7.3.1.2
Lane Width
The minimum lane width will be 4.9 meters (16 feet) in the inspection area. A preferred lane
width of 5.5 meters (18 feet) is recommended. The increased lane widths are required to
facilitate the manual inspection procedures and to support the potential for future automated
inspection technology. Outside of the inspection area the minimum lane width, facilitating the
flow of traffic and other operations, is 3.6-meters (12 feet).
7.3.1.3
Curbs and Gutters/Shoulders
Shoulders are desirable for accommodation of stopped vehicles (7, 20). However, curb and
gutter are preferable in areas where lane control is desired and to improve safety.
Therefore, shoulders are recommended for use in the approach roadways and vehicle holding
area. However, curb and gutter is required in the inspection area and around all
channelization islands.
7.3.1.4
Lateral Clearances
Lateral obstructions present a safety hazard and tend to negatively impact traffic flow. The
negative effects are eliminated or reduced if the object is less than 152 mm (6 in.) in height or
located at least 1.8 meters (6 ft.) from the edge of the roadway. Ideally this lateral
clearance would be greater. In the inspection areas, the location of facilities and inspection
equipment will likely provide less lateral clearance. Ideally, a lateral clearance of 610 mm
(2 ft.) should be maintained in the inspection areas where possible.
7.3.1.5
Vertical Clearances
AASHTO standards indicate a minimum vertical clearance of 4.3 meters (14 ft.) for highways
or 4.9 meters (16 ft.) for freeways. In order to support potential over height vehicles or
future pavement overlays a minimum vertical clearance of 5.2 meters (17 ft.) will be
maintained throughout the inspection facility. Higher clearance may be desirable for
inspection equipment.
7.4 Facilities
The facilities shall be developed in accordance with the guidelines provided in Section 4.12
except as modified in the following sections.
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