Lesson 1.0: The Anatomy of a Railroad Crossing

Your Basic Railroad Crossing: FRA #91650E at Milepost 25.29 on the BNSF Zap Line, north of Mandan, ND.

First step of recording a railroad crossing: don’t do it! 

*If an agency archaeologist and/or SHPO requires you to do it, then by all means, do as instructed but strenuously object!*

A bit of context:  Railroad (or grade) crossings are intersections where vehicular and/or pedestrian traffic crosses over a track(s) at the same elevation.  Crossings can be public or private.  Public crossings (county roads, highways, etc.) are usually governed by the public utility.  Private crossings are not intended for public use and are not maintained or governed by any public agency. All crossings are catalogued and issued a unique identifier (not unlike a license plate for a vehicle) by the Federal Railroad Administration (FRA). 

Your Basic Crossbuck: many BNSF Crossings have the FRA identifier placed on a larger sign with an emergency contact number facing the direction of vehicular traffic.

The identifier (generally found on a plate attached to one of the crossbucks) can provide useful information regarding the crossing.  The FRA maintains a public database of every crossing in the United States that includes, but is not limited to, the name/designation of the roadway, the railroad that owns the tracks & right-of-way at the crossing, average speed/number of trains on that particular track and the average number of vehicles that traverse the crossing in an average day.  The FRA also has an iOS crossing locator app which will allow you to obtain a crossing inventory report on your iPhone or iPad.

Crossing #91650E as depicted in the FRA Rail Crossing Locator App (iOS).

Detail View for Crossing #91650E in the FRA Rail Crossing Locator App.

Inventory Report for Crossing #91650E in the FRA Rail Crossing Locator App.

Given that railroad crossings must endure traffic in the form of both trains and automobiles, they are frequently the target of routine maintenance, repairs and, eventually, replacement.  Most of us, I suspect, have had our fillings rattled at one time or another as we drove over a railroad crossing that was in dire need of attention.  Compared to other features such as bridges, culverts or tunnels, the components that form a crossing are replaced frequently enough that the odds of you ever finding a crossing that meets the >50 year threshold are slim to none. 

If there are trains blasting through the crossing in question at speeds greater than 40 mph, there is zero chance that the crossing is >50 years of age.  Trains that travel at 40mph or greater place a great deal of stress on the track structure (crossings included).  This, in turn, requires a higher degree of maintenance and upkeep than trackage that only sees trains puttering along at 20mph or less.  

Most modern railroad crossings at light density crossings (private driveways, lightly-trafficked county roads, industrial crossings, etc.) are constructed of panels placed perpendicular to the rails and crossties that form the track.  The panels consist of ties in 8' or 16' length.  Most crossings are constructed with a width of 24' (One 8' Panel and One 16' Panel).  Two ties form a panel and they are held together with 3/4" steel dowels.  Each tie is 8 3/8" in width.  The height will vary from 7" to 8" depending on rail size (the subject of another future lesson).  The panels are secured to the cross ties with large timber (lag) screws with a pneumatic drill.  For further dimensions and details, see Page 59 of the BNSF Industrial Track Standards Manual [pdf].

Detail view of the crossing panels & timber screws at Crossing #91650E.  The crushed granite surrounding the ties is not native to the area and indicates that the sub grade has been cleaned & rebuilt.  Nothing remains of the original construction of the Zap Line at this location except for the right-of-way.

Many archaeologists who have recorded crossings use the date on the rail to gauge the date of the crossing.  While the date on the rail is accurate as to when it came out of the steel mill, it is highly inaccurate as a measurement of the age of the track and associated crossing.  Rail is recyclable and can be reused again and again before it finally gives out and is turned into rebar.  At Crossing #91650E, the south rail has a roll date of September 1948 and the north rail has a roll date of October 1972.  I will devote a future lesson to rails and explain various methods to date the rails/track structure.

Detail view of the south rail at Crossing #91650E.  It was rolled at Colorado Fuel & Iron (CF&I) in 1948.

Detail view of the north rail at Crossing #91650E.  It was rolled at Bethlehem Steel in 1972.

In sum: When someone does record a crossing, the staff at most SHPOs aren't aware of how to gauge the age of a crossing (or railroad infrastructure in general).  Since railroads have been deemed as 'old', they are virtually guaranteed to receive the rubber stamp of approval.  This usually starts a chain reaction of archaeologists adding other crossings in the area as updates to the original crossing.  In as little as three years, a single crossing can morph into a dozen crossings (and an 84 page site form) and become the bane of archaeologists from here until eternity.  

the chances of finding a railroad crossing in the U.S. that is 50 years of age or greater is on par with hitting it big in the lottery.  There are crossings out there that do meet the threshold but they are rare and you will most likely never see one in your travels as an archaeologist.  When in doubt, refer to the FRA Crossing Database or make contact with the railroad's engineering department.  If all else fails, contact me (hawkcoulee@gmail.com) and i'll try to help you out.

Next week: Railroads, Divisions, Subdivisions and Sections: How you can use them to establish Site Boundaries!