Thursday, June 13, 2013

6000 Bikes Per Hour

A few weeks ago, a sea of cyclists pedaled (slowly) through Cambridge. The city has two annual recreational rides, complete with police escorts, where hundreds of bicyclists take to the streets. I took a video of the procession through Inman Square and it got lost in my phone for a while, but recently resurfaced and made it to Youtube.

It's not that much to watch, unless you really like watching chatty cyclists at low speed, but it is illustrative how space-efficient cyclists are. The video lasts a bit shy of three minutes, and for about 2:30 of that (give or take) the swarm of cyclists passes by. I happen to know that there were about 250 (actually 258, according to the website). But let's use round numbers—even at low speed there were 100 cyclists passing by per minute.

Which is extremely efficient.

On a freeway, a lane of traffic can only carry at most 2000 vehicles per hour—beyond that the roadway devolves quickly in to gridlock (and the number of vehicles drops). Yet one lane of bicyclists can accommodate three times as many people—you'd have to have three or four people in every car on a freeway to have the same level of service. Want to fill buses? Fine, but you better be able to get a full bus through every 30 seconds to match a lane of cyclists. Rail can surpass this capacity—at rush hour the Red Line in Cambridge peaks over 10,000 people per hour, and some lines in New York go past 20,000—but you need a bit more infrastructure to run such rail routes.

Since bicycles take up far less space than vehicles, they use road space much more efficiently than vehicles. Even if a rate of 6000 per hour necessitates a police escort, it's still a testament to the efficiency of the bicycle.


  1. Buses running in a dedicated lane could probably manage 6000 passengers per hour, though it does require quite a lot of buses. Streetcars running in a dedicated lane could quite easily exceed it, given that they can be made longer than buses. And a full on metro can carry much more than 10,000 passengers per hour. By my calculations, the Moscow Metro can do about 45,000 per hour in dense, but not crush-load, conditions, at the peak service level currently provided. By comparison, the Red Line hs slightly shorter (but slightly wider) trains. The real problem though is the signal system, and possibly dwell time at the central stations, which limits the overall line capacity to 4.5 minute headways when 1.5 might be possible with the same tracks, trains, stations, and signalling technology.

  2. Good points, although all of those modes (except maybe buses) require orders of magnitude more infrastructure than bicycles.

    The Exclusive Bus Lane in the Lincoln Tunnel assuredly manages more than 6000 per hour (perhaps more than 20k). Subways in NYC on 3 minute headways at 2000 passengers per train carry 40k per hour; where they are stacked (the Lexington or 8th Avenue Line) one lane carries two tracks in the "space" of one lane and 60k-plus at peak times.

    Signals limit the Red Line, but crush capacity does as well. Once trains become at all bunched, dwell times increase and bunching exacerbates, slowing service for emptier trains behind. NYC trains which run express for two miles or more have more running and fewer stops which minimizes this issue.

    I'm wondering whether the new Longfellow (this is off topic and needs to be a separate post) could have two lanes; the right-most a wider bike lane in the mornings and on weekends, and a traffic lane in the evenings, when there is a worry about the bridge backing up in to Kendall Square and snarling traffic (and bus transit) there.