After a major toll highway introduced a system of electronic toll paying, delays at all of its interchanges declined significantly. Travel time per car trip decreased by an average of 10 percent. Tailpipe pollution for each trip decreased commensurately. Despite this, the total air pollution from vehicles on that highway did not decrease measurably. Which one of the following, if true, most helps to resolve the apparent discrepancy in the information above? ["Even after the switch to electronic toll paying, there were sometimes long delays at the highway's interchanges.", 'The prospect of faster, more convenient travel induced more drivers to use the highway.', 'Travel time on the highway for car trips under 30 kilometers (18. 6 miles) did not decrease appreciably.', 'The highway began charging higher tolls when it switched to electronic toll paying.']