Background and assumption for Table (see next page)
Carla, a commuter in San Francisco, travels 10 miles from her suburban home to the central city. The table assumes that Carla values the time spent on the transit vehicle at one-half her wage rate and values the time spent walking and waiting at one and one-half times her wage rate.
Her wage is $12 per hour. Hence, she is will to pay $6 to avoid one-half hour of in-vehicle time and $18 to avoid one hour of walking and waiting time. The translate into 10 cents per minute and 30 cents per minute, respectively.
Calculation of alternative modal cost of one-way commute:
1. Calculation of collection time cost of auto, bus, and Bart.
2. Line-haul time cost reflect the speed of travel by each mode.
3. Distribution time cost reflect time at destination to reach her place of employment (assumes she has parking at the front door of her employer)
4. Money cost is the operating cost plus fare or parking cost. Assume auto cost is $0.20 per mile, bus fare is $1, BART fare is $1.50, and half of $6 parking cost is allocated to the morning commute.
Note that the auto is the rational low cost mode compared with a bus.
How can we persuade Carla to switch from her auto to mass transit? Several possibilities:
1. Subsidized transit (free or bribe). Note that transit fare must decrease by a relatively large amount to offset the time-cost advantages of the automobile.
2. Line-haul time. Bus would have to decrease line-haul time from 50 minutes to <35 minutes.
3. Collection and distribution time. Bus would have to lower collection and distribution time from 15 minutes to <10 minutes.
4. Auto monetary cost. If operating cost of auto increased from 20 cents to 36 cents per mile. A congestion tax (or pollution tax) of 16 cents per mile would switch her to the bus.
5. Parking cost. If parking cost increased to at least $4.50 ($9 per day) she would shift to the bus.
6. Wage. If Carl’s wage dropped to $8, the bus would be less costly that the auto (as it lowers the opportunity cost of travel time.)
Commuters favor mass transit when:
1. The are located in close proximity to stops and stations.
2. They have a low opportunity cost (student, retired person, or low wage earner.)
3. Low walking cost. Persons who enjoy walking are don’t mine waiting.
4. Disutility of driving. People dislike the hassle and anxiety of driving, as opposed to driver ‘athlete’ who puts on the gloves to drive to work.
5. No automobile. People (poor) with no alternative to public transit.
Cost of Travel Modes and Modal Choice (based on initial assumptions)
Auto / Bus / BARTCollection time cost
Collection time (minutes) / 0 / 10 / 15Cost per minute ($) / 0.30 / 0.30 / 0.30
Collection time cost ($) / 0.00 / 3.00 / 4.50
Line-haul costs
Line-haul time (minutes) / 40 / 50 / 30Cost per minute ($) / 0.10 / 0.10 / 0.10
Line-haul costs ($) / 4.00 / 5.00 / 3.00
Distribution time costs
Distribution time (minutes) / 0 / 5 / 9Cost per minute ($) / 0.30 / 0.30 / 0.30
Distribution time cost ($) / 0.00 / 1.50 / 2.70
Money cost
Operating cost or fare ($) / 2.00 / 1.00 / 1.50Parking cost ($) / 3.00 / 0.00 / 0.00
Total money cost ($) / 5.00 / 1.00 / 1.50
Total time cost ($) / 4.00 / 9.50 / 10.20
Total Cost ($) / 9.00 / 10.50 / 11.70