Clearance.
—The New York State Highway Commission makes it a rule to secure the following clearance:
When a highway passes under a railroad the crown elevation is made 13.5 feet below the bottom of the bridge girder, and the minimum right angle distance between abutments is taken as 26 feet. The distance from the base of the rail to the bottom of the girder varies with the span of the bridge and ranges from 2 ft. 2 in. for a 30-foot span to 2 ft. 41⁄2 in. for a 110-foot span.
Where the highway crosses over the railroad a minimum clearance of 21.0 feet is required from the top of the rail to the bottom of the highway bridge girders. The span or right angle opening will vary with the number of tracks and the standards of the railways. It is, of course, well to have a clear opening over the entire used roadway. The practice in some places, of having piers or piles in the center of the road, unless there is placed around these a safety zone or park extending each way along the street so that traffic may be separated some little distance before coming to the pier, is not to be commended.