At first it may seem counter intuitive: what is wrong with a network of subway trains running fast, hitting destinations on time and generally being regarded as efficient? This is, after all, the “charge” leveled at London Underground. The reason, based on mathematical modeling, is that this will disincentivize people to travel by other means (car, bikes, or on foot) and draw them into going by subway train. The net effect, the model predicts, will be a marked increase in the overall level of congestion. Annual passenger numbers are already around 1.3 billion.
The model has been written into an article published in the journal Royal Society Interface. It is titled “Multiplex networks in metropolitan areas: generic features and local effects.”
Congestion will arise, the report explains, at intersections and stations where people wish to switch lines. These can easily become bottlenecks, very much due to the layout of the London tube network. In contrast, the report draws parallels with the world’s other great underground network: the New York subway. Here, the design prevents bottlenecks from occurring as often.
Speaking with the BBC, lead author Dr Marc Barthelemy said: “Surprisingly enough, the network in New York is much more centralized than the one in London.” This means that running trains faster in New York is more efficient, whereas running trains slower in London is likely to take the strain off stations that act as interchanges.
To counter the effects of current and future congestion, the report recommends underground trains running along the 150 year-old network should only travel at a rate of around 1.2 times faster than the average speed that cars move at on the roads. This reduces the typical Tube train speed to 13 miles-per-hour (21 kilometers-per-hour), well below the;current average speed of 21 miles-per-hour (33 kilometers-per-hour).
