As gas prices race toward $4 a gallon, metro Atlanta commuters who turn to transit are beginning to save some real money.

Given an average round-trip commute of almost 40 miles per day, the cost of driving alone to work is about $470 a month including gasoline, vehicle maintenance and wear and tear, according to a 2007 American Automobile Association study. And this doesn't include the cost of parking, insurance and car payments. Add those into the mix and the cost can soar to almost $1,000 a month.

As outrageous as that cost seems, it becomes even more so when compared with the cost of transit —- a monthly MARTA pass is $52.50; an Xpress coach pass is $80. Commuters have taken note of the tremendous savings that transit can offer, measured in both time and money, and in recent weeks a growing number of them have started taking transit.

Many of these new transit riders have enrolled in the Clean Air Campaign's incentive programs. One of them, Cash for Commuters, rewards commuters who have been driving alone to work when they agree to start using a clean commute alternative. Those who car pool, telework, ride transit, walk or bike to work earn $3 per day, up to $180 over an assigned 90-day period (www.commuterrewards.com/cash_for_commuters). Participation in this program is up 300 percent compared with last year.

And when someone who normally drives alone tries an alternative, the impact can be substantial. Not only do we get the immediate benefit of one less car competing for space on the metro region's maxed-out roadways, but we also benefit from less air pollution, as half of smog-forming emissions come from tailpipes. And many people who try a commute alternative like the positive effect it can have on their quality of life, and they stick with it. In fact, up to one year after their short-term financial incentive ended, 64 percent of people who previously drove alone have decided to stick with their clean commute.

Growing the ranks of clean commuters is also important for expanding our region's transportation options. A recent survey by the Transit Planning Board showed that support for a 1-cent sales tax to fund regional transportation is considerably stronger among those who use transit, even if that use amounts to only one or two trips in the past year (67 percent support versus 52 percent support for those who don't ride transit).

Denver voters approved a similar sales tax, as Atlanta business and civic leaders learned when we went there earlier this month. Denver —- a region with less than half our region's population, and expecting half our growth in the future —- has taken control of its traffic destiny and is in the midst of building 120 miles of new rapid transit. Public support has overcome political inaction, and the region is in the process of creating a top-notch transit network that enhances long-term economic viability and quality of life for its residents.

The same can happen in metro Atlanta. Now is the time to capitalize on our region's growing dissatisfaction with being stuck in traffic and paying dearly for it. We must continue to promote the use of the alternatives that are currently available, and in doing so create more support to push for more alternatives in the future. It could be our best bet for making real progress toward a traffic solution.

> Kevin Green is executive director of the Clean Air Campaign, a nonprofit organization that motivates Georgians to take action to improve air quality and reduce traffic congestion.