String charts aren’t new

 What’s a string chart? It’s a way of representing schedules, for trains in our case. The idea is pretty well known in model railroading. It is simply a graph of time vs. distance. The distance is the geography of a train’s run and the time span is that of its schedule for that run.

This is very clearly explained, indeed spelled out in detail, in Bruce Chubb’s excellent book, How to Operate Your Model Railroad (Kalmbach, 1977). The example below is for a notional railroad, running from Easton to Weston, and the train is No. 24. The slanting line connects (from bottom) the departure time at Easton with the times of the stops at Frog’s Hollow and Elbow Bend, to the arrival at Weston.

Thus the slope of the line is the average speed. The times in such a chart can come from, or be the basis for, a working timetable. When a complete schedule of trains is represented in this way, the advantage of a string chart is that it visually shows all trains in relation to each other, while showing location and duration of intermediate stops. 

I recently encountered an example of string chart that shows the idea is not new. Here’s the background. The Gotthard Tunnel in Switzerland, passing under the very steep St. Gotthard Pass of the Alps to reach Italy, was completed in 1882. It is 15 km (9.3 miles) long, at the time of its construction the longest tunnel in the world (today an even deeper St. Gotthard Base Tunnel is 57 km long.)

In 1982, as part of the centenary of the 1882 tunnel, a commemorative calendar was issued, including photos of the original construction and train photos of various eras. What I found interesting, though was a reproduction of the original schedule through the tunnel, expressed as, you guessed it, a string chart. 

Note at the bottom of the image above that the cover and interior pages of a travelers’ guide, in French and German. It can be seen in the pages at right that there were a lot of trains. For contrast, the 1982 schedule was reproduced also, as you see below. Still lots of trains.

I would just mention in closing that most model railroads with any complexity of train operation can benefit in planning as well as execution if string charts are constructed. My point today is that the idea is far from new, and certainly didn’t originate with model railroaders. 

Tony Thompson