[sustran] motorcycles and congestion

[Todd Litman]

Questions about motorcycle impacts come up fairly regularly. 

According to one study (published in Impacts of Heavy Freight Vehicles,
OECD (Paris), December 1982) motorcycles on urban freeways are estimated to
impose 0.5 passenger car units (PCU) of congestion when traffic per lane is
less than 600 vehicles per hour (VPH), but increases to 1 PCU at 1,800 VPH.

I generally believe that motorcycles, when correctly driven based on
developed country standards of traffic behavior, take the same amount of
space as an automobile, except for the infrequent times that two
motorcycles ride side-by-side, or when traveling at very slow speeds. Road
space requirements have little to do with vehicle size; it is primarily
defined by the need for reaction space. The faster a vehicle goes, the more
vulnerable the vehicle is, the more road space it requires. (That is why
roadway capacity decreases at traffic speeds over about 60 km/hr.)

In congested urban areas in developing countries, motorcycles often squeeze
closer together and take advantage of traffic gaps, so they probably cause
less congestion. I don't know of any research that quantifies this. Please
let us know if you find any.

Motorcycles are more fuel efficient than automobiles (averaging about 50
mpg according to the U.S. report, "National Transportation Statistics," by
the Bureau of Transportation Statitics, but I suspect that this has
decreased as large, prestigious motorcycles have taken over the market),
although their per-passenger fuel efficiency is somewhat less, because they
normally have only one passenger, rather than 1.5 for the overall vehicle
fleet. Motorcycles tend to be driven far less (2,600 miles per year, vs.
11,239 for automobiles), because most are used as fair-wealther luxury
vehicles. Thus, somebody who relies on a motorcycle instead of an
automobile probably saves fuel, but in practice, most motorcycles are owned
in addition to an automobile, and most of their use is discrtionary.

Motorcycles are cheaper to purchase than an automobile, but because they
have high insurance costs and are driven less on averge than an automobile
and average fewer passenger, their average cost per passenger-kilometre is
high.

Motorcycles do not have good air pollution controls (a catalytic system
could literally burn the pants off the rider), and their noise pollution is
particularly high, although this is partly a matter of style (a classic
case of animals using noise to establish territory during their aggressive
stage). Relatively quiet motorcycles are available, they just are not as
popular.

Motorcycles can reduce parking requirements. They can typically be parked
in 1/2 the space as an automoible, although some motorcyclists prefer to
use a full parking space.

Motorcycles have very high crash costs, partly because riders are quite
vulnerable, and partly because people who choose to ride a motorcycle tend
to be risk-takers.

My owe conclusion is that the only legitmate social benefits of motorcycles
are that they are somewhat more fuel efficient, and they are more
affordable to purchase and thus provide mobility to some lower income
people, but both of these benefits are slight.