One of the most frequent criticisms of Dallas’s light rail implementation is that it carries comparatively few riders for the amount of track that has been built. This is then followed by either criticism of suburban-oriented transit generally, or by praise for Houston’s more urban-centric system.
Recently, it occurred to me to look up the ridership per mile of the Shinkansen network. Using annual figures (since the Shinkansen has a different weekly distribution than commuter-oriented LRT), the bullet train carries 340 million people over 1484 miles of track. DART carries 28.5 million people over 85 miles of track.
That gives the Shinkansen an annual ridership per route mile of 229,101, while Dallas clocks in at 336,096.
Is Dallas’s light rail 50% more effective than the bullet train? It is if you use the same math Houstonians have been using to argue why our system is better than the big D’s.
Clearly, a new metric is needed. I propose that we evenly weight both speed and ridership density. Density, because a system that serves denser-developed areas is more effective than one that serves a few desolate park and ride lots. Speed, because a system that gets you there faster is better than one that’s slow.
Distance-Normalized Ridership takes passenger volume, divides by system length, and then multiplies by space-mean speed. If all other factors are held constant, this number can be raised by an increase in ridership, an increase in average speed, or a decrease in total system length. This also captures one of the most basic tradeoffs in transit planning; do we have more stops, and serve a greater area? Or do we have fewer stations, to provide a faster trip? Finally, Distance-Normalized Ridership also has the advantage of being constant across Metric and Imperial units, because the distance factors cancel each other out. I propose that Distance-Normalized Ridership be expressed in units of riders per hour squared.
To show how this works, let’s look at Houston and Japan.
The combined ridership of the Tokaido, Sanyo, and Kyushu Shinkansen lines between Tokyo and Kagoshima is 219,513,000 passengers per year. This line stretches across 1326 kilometers and takes approximately 6.5 hours to traverse, for an average speed of 204 kilometers per hour.
Dividing 219,513,000 into 1326 yields 165,545 annual riders per kilometer. Further division yields 18.95 hourly riders per km. Multiplying this figure by 204 km/h yields 3866 riders per hour squared, which sounds like a reasonable number. The statistics for the Tokaido Shinkansen alone are 6337 riders/hr2, reflecting the much higher ridership density on that segment.
As of this writing, Houston MetroRail carries 45,751 riders on an average weekday, plus 18,656 on Saturday and 14,494 on Sunday. This adds up to 261,905 every week, or 1,559 per hour. Dividing 1,559 into the system’s 12.8 mile length yields 122 hourly riders per mile, and multiplying by its average speed of just over 15mph yields 1871 riders/hr2.
These numbers make intuitive sense. Japan’s Shinkansen is twice as effective as MetroRail, and the core Tokaido Shinkansen is twice as effective as the network as a whole. The figures are small enough to not be unwieldy (e.g. we’re not talking millions), yet large enough that we can get a reasonable degree of accuracy without using a decimal point.
So what about Dallas? I’m not going to compute them for this post. First, because I’m more interested in proposing a new metric than in producing yet another 713-214 comparison. Second, because I’m unsure of how to weight Dallas’s various lines. DART’s slowest segment also has the most interlining, and how you weight that is a major determinant in systemwide average speed.
What I’d really like is for some outside party – say, Greater Greater Washington’s Matt Johnson – to tally up the distance-normalized ridership for Dallas, Washington, and a number of other systems. I have a feeling WMATA would score fairly decently, given that system’s relatively high speeds.