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156 On all bridges the lateral distance. from the face of the curb to the face of the bridge rail or any structural member shall be at least 18 inches and as much more as is necessary for walk space, which shall be provided on all long bridges.

On short bridges the lateral distance from the edge of the pavement of the approach highway to the face of the bridge rail, any structural member, or the curb shall be not less than the width of shoulder on the approach highway.

On sections of the system improved with divided highways, one bridge to accommodate both roadways and the median strip or two separate bridges, each to accommodate one roadway, may be used. On short bridges the two roadways shall be accommodated without deviation from their normal alinement, and on long bridges the two roadways shall be so accommodated if feasible.

Where, on long bridges, the median strip is reduced in width, the change in alinement shall be accomplished in such manner and over such lengths as will avoid hazard in vehicular operation at the design speed and the appearance of distorted or forced alinement. Where the median strip is reduced in width over structures the two roadways shall be separated by a raised, but mountable, dividing strip not less than 4 feet wide.

Auxiliary lanes on bridges.—Where auxiliary lanes or designs for other purposes provide a pavement over bridges that extends more than 3 feet outside the normal edge of through-traffic lanes, the vehicular curb shall be continuous with the curb on the approach highway; or in the absence of an approach curb, the vehicular curb shall be located at least 2 feet outside a line extending from the edge of the widened pavement on the approach.

Bridges on curves.—On all bridges on curves the clearances shall be at least as great as those required for all other bridges, and the lateral clearance to the face of the bridge rail or any structural member shall be as much more as shall be necessary to maintain the minimum sight distance used in the design of the section of highway on which the bridge is located.

Clear height of bridges.—The clear height of all bridges over the entire width between outer curbs shall be not less than 14 feet.

Openings under bridges.—All bridges over railways shall provide a clear height and length between abutments to be determined by agreement with the railway companies concerned.

All bridges over public roads or highways shall provide a clear normal distance between abutments not less than the sum of the widths of the surfaces or pavements, median strip and shoulders or sidewalks of the underpassing road or highway, such distance to be clear of all obstruction except that a central pier may be founded within the median strip of a divided underpassing highway if the sides of such pier, parallel to the direction of the underpassing highway are not less than 4 feet from the inner edges of the adjacent pavements. All bridges over roads or highways shall provide a clear height above the surface or surfaces of the underpassing road or highway of not less than 14 feet, and of not less than 12 feet above the outer edges of the shoulders of such highway.

Pavements on bridges.—All portions of bridge pavements, between lines joining the edges of the pavements of the approach highways at the bridge, shall be of a color identical with that of the pavement on