Politicians on the west side of Salt Lake County don't want a toll road. That message has been sent loud and clear, and re-emphasized recently with city council resolutions.

Less clear, however, is how those politicians would pay for the Mountain View Corridor, a new highway needed for the rapidly growing west end of the county. Gas-tax increases are unpopular and ineffective, especially as cars become more fuel-efficient.

A form of tolling known as congestion pricing seems to be the most effective way to finance highway construction. Those who oppose such a plan ought to consider just how much traffic congestion is costing them already. People who regularly idle their engines in rush-hour traffic pay for that privilege, whether or not they realize it. The community pays, as well, through increased pollution and through a slow-down in the movement of goods and services. Meanwhile, Utah's freeways are lightly used during non-peak hours. People who complain about empty off-peak TRAX trains or UTA buses seldom bother to consider the cost of empty freeways during many hours of the day — freeways that cost taxpayers the same to maintain all day long.

The Utah Taxpayers Association recently compiled figures from the Federal Highway Administration that show 69 percent of Americans who drive during afternoon rush hour are making discretionary trips. That is, they could instead be driving during off-peak hours. In the morning, 56 percent of the rush-hour trips are discretionary.

Congestion pricing would give those people incentives to drive at other times. It would change the amount of the highway toll depending on the amount of congestion. Using electronic devices, drivers would be charged automatically, eliminating stops at toll booths. This would even out the traffic load throughout the day. The added benefit for drivers is they no longer would be wasting gas while stuck in traffic, a savings that would offset part of the toll.

We understand the argument that the west side feels it is unfair to have a toll road while east-side freeways are free. That is a compelling concern. The solution would be to impose a congestion-price scheme on I-215 along the east bench, as well. That may require some changes in law.

But with federal highway money disappearing, and with gas taxes losing their ability to effectively raise funds, congestion pricing seems the best alternative available, regardless of what west-side politicians think.