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Pollution: Facts and Figures

Chicago Ill.: Cost effectiveness of different strategies to reduce hydrocarbon
emissions compared: 

     Secure bike parking at rail stations:   $311 per ton
     Commuter rail car-pool matching:      $3,937 per ton
     Express park and ride services:      $96,415 per ton
     Feeder bus services to stations:    $214,959 per ton

As of January 1, 1985, air pollution emissions factors per mile for the
average vehicle in the US include:

      3.33 grams volatile organic compounds       (hydrocarbons)
     27.52 grams Carbon monoxide
      2.0 grams Nitrogen oxides

But, for trips of two miles or less, 100% cold start on an average 75 degree
day those same figures are:

       5.7 grams HC   up 73%
      57.52 grams CO -- up 109%
       2.52 grams NOx   up 26%

Cold starts and the lower average speeds associated with short distance car
travel bear a heavy responsibility for pollution, and these are precisely the
journeys that could easily made by bicycle.

[63% of all trips in the US are 5 miles or less -- USDOT]
--How To Promote Bicycling as a Pollution Solution, (June 1989), League of American Bicyclists


Average Speed Category (mph)     Annual Miles                                 


5                                 26,000
10                                65,000
15                               320,000
20                               300,000
25                               200,000
50                               310,000



Average Speed Category (mph)    CO Emissions (grams/mile)

5                               140
10                              100
15                               70
20                               55
25                               45
50                               25



Mean Trip Length       Relative Fuel Economy

1/4 mi.                .1
1                      .25
3                      .45
4                      .55
5                      .60
6                      .65

--Marda Formann Mayo, Bicycling and Air Quality Information Document, prepared for USEPA by Abt Associates, Sept. 1979.

Trip Length Distribution of 
Existing Midtown Bicycle Trips (Table B-4):

Trip Length Range               Percent of Trips of This Length
(miles)                          Each           Cumulative

0 to 1                           3.3              3.3
1 to 2                          16.7             20.0
2 to 3                          28.0             48.0
3 to 4                          40.0             88.0
4 to 5                           8.0             96.0
greater than 5                   4.0            100.0


Potential Daily Bicycle Work Trips by Previous Mode (Table C-2):

Previous Mode            Potential Bike Work Trips

Auto driver                    950
Taxi                         5,600
Subway                      20,300
Bus                         32,400

total                       59,250

[If there were bikeways separated from motor vehicle traffic and sufficient
bicycle parking. Their estimate conservatively provides that all switched
trips would be under 2 miles. --dc]

--Route Report, Manhattan Commuter Bicycle System Study, July, 1978. Prepared for: NYC DOT; Prepared by Edwards and Kelcey, in association with Transportation Alternatives.

125,000 Btu/gal. of gas
-----------------------     =   1136 mi/gal for bicycle
110 Btu/mi. to ride bike

125,000 Btu/gal. of gas
-------------------------   =  250 mi/gal for walking
500 Btu/mi. to walk
energy content of gas -- Tri-State Planning Commission bike energy use --
Hirst, E. walking energy use -- Dougherty, N. and Lawrence, W.


Energy Consumption of Various Transportation Modes (Btu/pasgr.mi.)

Mode       Full Capacity             Present Occupancy

Auto          1,635                      6,000
Rail          1,000                      4,250
Subway          750                      3,150
Bus             650                      2,500
Walk            500                        500
Bicycle         110                        110

motorized data -- Tri-State Planning Commission, Regional Propulsion
Efficiency of Tri-State Ground Modes of Passenger Transportation,
March, 1975.


Estimate Impacts of an Auto to Bicycle Mode Shift of One Percent of NYC
Traffic [on local roads and arterial] (Table 4-2):

Factor   Annual VMT        Savings                  Total 
          Reduction          per mi.              Savings
Fuel     38,706,570        .07 gal          2,709,000 gal
CO       38,706,570      41.5 grams     1,606,000,000 gr
HC       38,706,570       4.2 grams       163,000,000 gr
NOx      38,706,570       3.8 grams       147,000,000 gr 
[these figures are underestimated due to not factoring in cold starts on these
shorter trips, which yields lower gas mileage and more pollution per mile --

--Bikeway Planning and Policy Guidelines for NYC, Manhattan Commuter Bicycle System Study, July, 1978. Prepared for NYC DOT; Prepared by Edwards and Kelcey, in association with Transportation Alternatives.

However, automobiles are considerably less fuel efficient on short trips, which will be the ones most likely to be diverted to the bicycle. Studies have shown that for the average bicycle trip length of about two miles, the relative fuel economy would be 35% of the overall fleet average. (T.C. Austin and K.H. Hellman, "Passenger Fuel Economy as Influenced by Trip Length," a paper presented at the Automobile Engineering Congress, Detroit, February 1975.)

--Bicycle Transportation for Energy Conservation, a report of the Secretary of Transportation to the President and the Congress, April 1980.

In addition, contact the Chicagoland Bicycle Federation (312)427- 3325. They successfully pressured their regional transportation agencies to spend most of their CMAQ money on bikes. Their work proved that bikes reduce the most pollution per dollar spent, largely because of cold starts.


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Last updated: 7 April 1999