With the growing congestion on Wasatch Front freeways - as any motorist knows who tries to drive during rush hours - the Salt Lake County commission needs to hold a special election next November to find out if voters will approve a quarter-cent sales tax to finance a light-rail system.

Despite efforts to get the county to wait a year on the election, this is not an issue that would benefit from delay.Every study of the valley agrees that population and commuter growth in the next decade will push the highway system into traffic gridlock unless alternate transportation systems are introduced. And a light-rail system is not something that can be built overnight.

The Utah Transit Authority is proposing that a 12-mile light-rail line be constructed between Sandy and downtown Salt Lake City for an estimated $150 million. Another $75 million would be spent to improve I-15 and expand UTA bus service. The sales tax would produce about $17 million a year to finance the improvements. Federal funds also would be sought for the light-rail system.

None of this is particularly complicated and there are several reasons for acting as expeditiously as possible. But opponents of the light-rail idea, particularly the Area Leaders for Responsible Transportation, or ALERT, are seeking to delay the decision.

Officials of ALERT want the County Commission to put the issue on the 1992 general election ballot instead of holding a special vote in November 1991, a non-election year. They say the average voter doesn't understand the light-rail issue and a non-election year ballot would produce a small turnout.

It's true that the turnout for special elections can be disappointingly small, but it depends on the issue. A proposed sales tax hike dealing with transportation - something everybody understands - could and should produce a significant voter response. Besides, the lack of other distractions on the ballot certainly should focus voters' attention.

The six months to go until next November should be plenty of time to acquaint voters with the pros and cons of the issue. Seeking an additional year to fight against the light-rail plan looks suspiciously like a reaction to polls that show a majority of county residents favoring light rail.

There are other reasons for immediate progress on light rail.

First, the competition for federal funds for transit systems is growing. Some 30 cities have projects in the planning stage and almost every city that already has light rail is proposing expansion of the system. At the same time, federal budget deficits are sure to shrink available funds.

Second, delay itself is expensive. Depending on inflation, each year can add between 5 and 10 percent to the cost of the project. And the extra cost to taxpayers doesn't produce one additional benefit.

Third, state and local officials need to know as soon as possible how far they should go with expensive planning and engineering studies.

The County Commission should act quickly to schedule a special election next November. Sooner or later, Salt Lake County will have to build a light-rail corridor. And sooner will be better and cheaper than later.