of the approach pavement, the lateral distance from the outer edge of the approach pavement to the face of the bridge rail or any structural member of the bridge shall be 3 feet 6 inches.
On short bridges over streams, railways, and minor intersecting roads and streets, 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 or the emergency standing area 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 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 2 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 and_ public streets, roads, or highways shall provide a clear height and length between abutments or piers as hereinbefore recommended for bridges on rural sections of the system.
Pavements on bridges.—All bridge pavements shall be constructed as hereinbefore recommended for bridges on rural sections of the system.
Structural design of bridges.—All bridges shall be structurally designed as hereinbefore recommended for bridges on rural sections of the system.
Width of culverts —The over-all clear width of all culverts shall be equal to the sum of the widths of the surfaces or pavements, median strip, and shoulders or emergency standing areas of the section of the interregional highway in which they are installed.
On divided highways the two roadways shall be separated, over culverts, by a median strip of the width provided om the highwe approaching the culvert. In the case of culverts supercharged with an earth embankment, shoulders or emergency standing areas, and slopes shall be carried over the culvert, identical in design with the cross section of the approach highway.
