ROY -- If another lane is built on Interstate 15 through Weber and Davis counties, the biggest impact will be noise.
On Thursday night in Roy, the Utah Department of Transportation held the first of two public hearings on its plan to extend the state's express lane system throughout the Top of Utah.
A second hearing is set from 4:30 p.m. to 7 p.m. Thursday at Woods Cross City Hall, 1555 S. 800 West.
UDOT is conducting an environmental study on a project that will add express lanes from Interstate 215 in North Salt Lake to U.S. 89 in Farmington, and from Hill Field Road in Layton to the junction with Interstate 84 in Riverdale.
The new lanes would total 21 miles on both the north and south sides of the freeway and would make more room on I-15, particularly for carpoolers.
When the project is finished, it will connect approximately 80 miles of express lanes from Spanish Fork to Ogden.
UDOT Region One spokesman Vic Saunders said the state has been conducting the environmental study for the past 15 months.
The new lanes could bring up to an additional 1,600 vehicles to the freeway in the two counties during peak traffic times. And more vehicles means more noise, said Catherine Jones, express lanes project manager.
"Whenever you add another lane to the freeway, you have to address noise," she said.
Residential areas affected by the noise will be eligible for a noise mitigation study, Saunders said.
UDOT could eventually build up to six new sound walls as a result of the project.
Kent and Marlene Wright live within a "stone's throw" of the freeway in Roy. They are worried that more noise could affect the value of their home.
"We've already got all these billboards that shine bright light into our house, and now we could potentially have a lot more noise," Kent Wright said.
But aside from noise and commuting impacts during construction, the project's footprint is relatively minor.
All construction work would take place in UDOT-owned right of way. No wildlife, business or residential properties would be affected.
Saunders said that after final environmental clearance is granted, construction would likely begin in summer 2014.
UDOT officials say express lanes provide for better, more efficient use of existing highway resources by encouraging carpooling.
Solo drivers who want to use the express lanes can purchase an electronic transponder that tracks their use of the lanes.
For more information about UDOT's express lanes program, visit www.udot.utah.gov/expresslanes.
Residents can submit comments on the project through the website until Dec. 8.