[sustran] motorcycles and congestion

[Todd Litman]

At 08:48 AM 7/15/98 +0100, J.H. Crawford wrote:
>Todd Litman said:
>
>>My own 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. 
>
>I would take partial exception to this. In the developing nations,
>small (+/- 70 cc) motorcycles are commonly the first transport upgrade
>bought by families after they have a bicycle or two. These motorcycles move 
>in  great swarms in the Asian capitals and have got to be much more space
>efficient than cars. They almost always ride at least two abreast and
>don't pay much attention to lane markings. They are, of course, noisy, 
>and most of the machines of this class are 2-stroke, so the pollution they 
>create is terrible. The picture is different in the developed nations and
>accords with Todd Litman's description as far as I am aware.

I agree that motorcycles impose less congestion at lower traffic speeds.
Motorcycling allows lower income households to afford motorized transport.
It is certainly a benefit to those households, but the social benefits are
mixed. Pollution is certainly a problem. An even greater problem, in my
opinion, is the accident costs, which are extreme in many developing
countries. I suspect that to some degree high levels of motorcycling in
developing countries represent a "social trap" (a situation in which
individuals' benefits are in conflict with society's benefits), since once
streets become crowded with motorcycles, conditions for pedestians,
bicycles and public transit often suffer. It may be possible that total
benefits would be greater from transport policies that encourage more
public transit, bicycling and efficient land use solutions to
transportation problems in developing countries.


By the way, some of you may be interested in estimates of the congestion
impacts of bicycles. The table below is based on the standard U.S.
reference for traffic engineers, "Policy on Geometric Design for Streets
and Highways," AASHTO (Washington DC), 1990.

Passenger-Car Equivalents for Bicycles by Lane Width 

				< 11 ft. Lane		11-14 ft.	> 14 ft.
				-------------		---------	--------
	Riding With Traffic		1.0		0.2		0.0
	Riding Against Traffic	1.2		0.5		0.0



Below is the discussion of bicycle traffic impacts from my report "Whose
Roads? Defining Bicyclists and Other Non-Drivers' Rights to Use Public
Roadways", available from our Institute. This reflects developed country
condtions; there may be some differences in the more chaotic traffic
conditons in developing countries, but I suspect that most arguements would
apply almost everywhere.


=====================================================================
Congestion Impacts

Bicycles are sometimes considered a problem if they increase traffic delays
and accident risk. For analysis of bicycle traffic impacts, road conditions
are divided into four classes:

1. Uncongested roads or separated paths. 
 Bicycling on an uncongested road or path contributes little or nothing to
congestion.
 
2. Congested roads with space for bicyclists.
 Bicycling on the road shoulder (common on highways); curb lane (common on
newer urban streets); or a bike lane contributes little to congestion
except at intersections and driveways where other vehicles' turning and
lane shifting maneuvers may be delayed. 
 
3. Narrow, congested roads with low speed traffic.
 On narrow, congested roads, bicyclists who keep up with traffic probably
contribute less congestion than an average car, due to their small size and
maneuverability.
 
4. Narrow, congested roads with moderate to high speed traffic.
Bicycling on a narrow, congested road when the rider is unable to keep up
with traffic can contribute to traffic congestion, depending on how
difficult it is for faster vehicles to pass. 
 
Bicycling does not contribute excess congestion (more than other vehicles)
under the first three conditions. Under those conditions, a bicycle trip
that displaces an automobile trip reduces congestion overall. Under
condition #4 bicyclists can increase traffic delays and conflicts. How much
this actually occurs depends on the availability of alternative routes and
specific traffic conditions, but overall this represents a small portion of
bicycle transport mileage because cyclists usually avoid riding in such
conditions. Indeed, bicycling is forbidden on urban freeways where
congestion costs are highest.

Of course, other vehicles delay traffic. Trucks, delivery vehicles, farm
equipment, and automobiles operated by elderly drivers probably cause more
traffic delay than bicycles. If delay justifies excluding bicycles, these
vehicle classes should be prohibited too. 

Existing traffic law if observed by bicyclists and drivers minimizes
conflicts and accident risk. Slower vehicles are required to ride to the
right side of the roadway to facilitate passing by faster vehicles and to
get off the roadway when delaying five or more vehicles to let them pass.
Excessive conflict between bicyclists and motor vehicles therefore suggests
that either traffic laws are not being enforced or that facility
improvements may be justified to provide more road space or alternative
routes for bicyclists.

In summary, there is no evidence that bicycling increases overall traffic
congestion, delay or accident risk (considering both increased and reduced
congestion caused by bicycling), or that conflicts which develop between
bicycles and motor vehicles can not be effectively resolved using existing
laws and planning strategies.
=====================================================================



Sincerely,

Todd Litman, Director
Victoria Transport Policy Institute
"Efficiency - Equity - Clarity"
1250 Rudlin Street
Victoria, BC, V8V 3R7, Canada
Phone & Fax: 250-360-1560
E-mail:      litman at islandnet.com
Website:     www.islandnet.com/~litman