THE COSTS of making necessary transportation improvements around the country have not diminished during this administration, but hopes for progress certainly have. President Reagan has ruled out any increase in the federal excise tax on gasoline for the time being--even though Transportation Secretary Drew Lewis has been lobbying for an increase as a critical and logical federal approach to a balanced transportation policy. Not only is the president's decision bad news for all states desperate to finance road repairs and/or transit construction, but it also fails to make much financial sense.

In arguing for the increase, Mr. Lewis had noted that gasoline taxes are simply user fees, "which make sense in transportation" and which are "totally consistent with the direction of this administration." He cited aviation and inland waterways as examples. There is no question that transportation does need more money--and that there is not enough in the highway program to do the job. Mr. Lewis had recommended that a portion of the additional revenue be used for mass transit, which would have responded to the balanced road-and- transit approaches of the states.

Even members of Congress up for election and wary of tax increases have been supporting an increase in this gasoline tax, which has been the same for 23 years. Still, President Reagan said this week that he knows the need is critical but he does not believe the administration should be talking about tax increases when it is trying to get budget cuts through Congress.

Why not? What is inconsistent about cutting spending and raising revenue at the same time? One way or another, taxpayers will have to pick up the tab for road and transit costs, and an increase in a federal "user fee," in the form of a gasoline tax, is sound, politically defensible and long overdue.