However, in the book City Cycling, the concept of effective speed is explored... and the author makes an interesting assertion:
"Effective speed is calculated using the standard formula: speed equals distance divided by time. However, in this calculation, all the time costs are considered. For car drivers, a significant (and usually ignored) time cost is the time spent at work to earn the money to pay for all the expenses associated with the mode of transportation."
How much time does a motorist spend at his job, to earn what he spends on car payment, fuel, tires, maintenance, insurance, etc.? When I thought I needed a car as a teenager, my father accurately observed that I'd spend every penny I earned at a part-time job, supporting my transportation so I could get to and from that job. Some people grow out of that situation... others don't.
If you want to get even fancier, some transportation scientists came up with the concept of Social Effective Speed, which also involves "external" costs such as pollution and congestion, as well as direct costs.
Most motorists would just as soon ignore "effective speed" as they zoom past the toiling cyclist. Ha!