CONSEQUENCES TO HIGHWAY USERS

CONSEQUENCES TO HIGHWAY USERS

Costs of Motor-Vehicle Operation:

            There is no single correct answer to the question: what does it cost to operate a motor vehicle? In the first place, the elements to be included in cost differ, depending on the purpose of the question and the viewpoint to be taken. Secondly, although much is already known about motor-vehicle costs, much is still to be determined by experiment and observation.

            Some operating expenses increase more or less directly with miles driven; in other words, their cost per vehicle-mile is relatively constant. In this classification fall such items as fuel, tires, oil, maintenance and repairs, and that portion of depreciation attributable to wearing out. Other costs vary mainly with time and are constant for a given period such as 1 yr; or, stated in costs per vehicle-mile, they vary inversely with the number of miles driven annually. Included here are drivers’ license and registration fees, garage rent, insurance, and obsolescence, which is the portion of depreciation that results from inadequacy or being out of date. Some items are dependent entirely or in part on speed. The most important of these is the travel time of operator and rider; any charges for these will vary inversely with speed. On, the other hand, some of the operating costs that vary primarily with miles driven, such as fuel and oil consumption and tire wear may also be influenced by speed and other factors such as roadway congestion.

            Of the costs mentioned here, running costs that vary primarily with mileage or speed are most often affected by highway improvements. It follows that these are of particular concern in highway economy studies, for justification of many highway improvements depends largely on savings in operating costs to offset proposed expenditures. However, care must be exercised to consider only those costs or savings that are relevant to a particular comparison. Stated differently, only those costs or savings that will be affected by the proposal should be included in economy studies. The importance of this distinction is made apparent by the fact that, although the average cost per mile of owning and operating a standard-sized automobile is 13.6, the incremental or running cost of driving an additional mile is in the range of 5.

            The motor-vehicle running costs presented here were abstracted from data developed primarily by Winfrey and Chaffey, and were updated by Curry and Anderson. Because of space limitations, with a few exceptions, the detailed information given here is only for passenger cars. No single multipliers are appropriate to convert the costs among vehicle types, since they would vary substantially, depending on the particular maneuver for which costs are desired.

Table 4-2.        First approximations of multipliers to determine running costs for other vehicle classes from those for passenger cars.   

Vehicle Class
Operating condition	5,000 lb Pickup	12,000 lb Single unit truck	40,000 lb Gasoline-driven truck (2-S2)	50,000 lb Diesel-driven truck (3-S2)
Continuous travel on relatively straight and level roadways.	1.15	2.0	2.8	3.2
Added costs for idling, and slowing or stopping and accelerating	1.15	2.5	9.0	11.5
Added cots for travelling curves and corners	1.15	2.2	6.0	6.0