But West Valley residents at the state's freeway plan open house did say that traffic is bad enough already to justify the freeway. The road would run through the valley south into Utah County and join Interstate 15 around Lehi.

"I've kind of resigned myself - they're going to make a freeway," said Jeanmarie Goodman, a parent whose children walk across the proposed freeway alignment at 5800 West to get to Hunter High School. Her major fear is the planned crossings at freeway interchanges, not air pollution from the stream of vehicles moving past that school.

"I want my kids to live here, and with more people living here they're going to need more roads," she said after hearing the plans. "And if all these people live here, there's going to be pollution."

Others said it doesn't have to be that way if the Utah Department of Transportation would just wait for light rail or another mass transit line to serve north-south travelers in the western valley.

Utah's transportation planners have repeatedly underestimated ridership that new mass transit projects will attract, said Marc Heileson of the Sierra Club. They've done it again here, he argued, by calculating that such a rail line wouldn't do much better than half the 20,000 riders that the Sandy-Salt Lake City TRAX line attracted when it opened in 1999. The low expectations come despite assumptions of denser west-valley development by 2030 and the prior construction of rail spokes to South Jordan and West Valley City.

Meanwhile, the proposed freeway would run within a half-mile of 21 schools, and directly through school property in two cases.

"We've been going door-to-door in a lot of these neighborhoods making families aware . . . it's going to pollute the air your kids breathe," Heileson said. "Even if the freeway misses your house, it'll hit your kids."

Utah Moms for Clean Air founder Cherise Udell clutched a small child at the meeting while railing against any alignment near schools. The problem should be clear to West Valley City parents with children who would spend their entire educations near the freeway, she said.

"Kids who go from Hillside Elementary to Hunter Junior High to Hunter High School will go K-through-12 in a cancer corridor," she said.

In a telephone interview, West Valley City Mayor Dennis Nordfelt said the pollution argument against the freeway doesn't add up.

"It's amazing to me that people would think cars traveling 55-60 mph would generate more air pollution than cars idling and waiting to get through major intersections (on 5600 West)," he said.

He supports both the freeway and light rail, which under UDOT's plan would run down the center of 5600 West and not along the freeway at 5800 West.

"Neither of them can come too soon, and it doesn't matter which one comes first," he said.

UDOT project manager Teri Newell this week told The Salt Lake Tribune's editorial board that the freeway would meet current U.S. Environmental Protection Agency air standards. The government does not have air standards specific to highways near roads, she said, though EPA and the Federal Highway Administration currently are studying the effects of highway proximity to schools.

Utah Transit Authority official Mick Crandall fielded pointed questions from activists at the open house who wanted to know why planners wouldn't try light rail before a freeway. He acknowledged that transit ridership projections are conservative, but said even fully loaded trains running up and down the valley's west side wouldn't alleviate the need. When driving roughly along the planned alignment to the meeting Wednesday afternoon, he said, he was stuck in traffic for a half-hour between 1300 South and 4200 South on 5600 West.

"They need some roads over here," he said.

A 52-year resident of 3100 South in West Valley City said the stop-and-go traffic by her house will only get worse with growth, unless there's a freeway. Yulene Rushton said she remembers when only about five cars a day drove her now-gridlocked street.

"We do need another road," she said. "Everything along there is so bad."

bloomis@sltrib.com