Numbering Bridges and Tunnels

Along the track, overhead and undergrade bridges, as well as tunnels, have a reference number. This number usually indicates mileage to the 1/100th from wherever milepost 0.0 is (or was, e.g. Jersey City PRR to Philadelphia). But sometimes, the # is sequential (1,2,3,3A, etc.) What, if any, North American RRs still use sequential structure numbering, as is AFAIK still used today in the UK? I know NYC and DL&W did, and retained them through PC and EL until CR and the commuter RRs introduced mileage-based numbering. Farther back in history, other US RRs such as PRR were sequential; perhaps *all* were originally.

All lines that I know of around this way are numbered corresponding to the milepost to the exact 1/100th of a mile as you mentioned, except for catenary poles on Amtrak's NEC, which are marked as the milepost and then sequential order.

I agree with CSX, the tunnels and bridges are numbered with a MP location, although most have a name, used instead of a MP location. No one says I am at tunnel 64, they might say "I am at Musconetcong, or Bellewood", though. Black Rock, West Point, Kingston, Haverstraw, etc., ones I remember by name, never by MP. Mileposts are used by the MOW guys. Crews use names, from what I have seen, everywhere I have ever worked. Bridges are somewhat different. Sometimes named for the creek, river or water underneath them, sometimes by MP, sometimes a bridge has a name that defies explanation. not the case, with the "Sayre footbridge" though !!!

Regardless of a name, almost every railroad bridge (underpass or overpass) or tunnel has a number. AREMA recommends, and most railroads now follow, the practice of numbering them by milepost and hundredth.

The New York Central at one time numbered them consectutively by mile, with a subdivision letter in front of the mile on some branches. ("W" for Wallkill Valley Branch, "C" for Catskill Mountain Branch, etc.) The D&H did the same thing up to the 1920's. D&H, then Penn Central and Conrail standardized on PRR practice, which makes the most sense, of milepost and hundredth.

Ironically, the Ulster and Delaware numbered their bridges by mile and hundredth, with a "B" following the number for a bridge, and "C" for a culvert. The NYC changed all that when they bought the railroad in 1932, then Penn Central changed back in 1968.

The B&O numbered bridges by milepost and a letter, as 12A and 12B. When they inserted bridges, they became 12A-1/2 and 12A-3/4. That was awkward, and CSX adopted the subdivision code, mile and hundredth.

The Milwaukee had the strangest system. They numbered bridges with odd numbers, consecutive from Chicago. Culverts had even numbers in the same scheme. So Culvert 24 might be in between Bridge 13 and Bridge 14. Go figure.