SOLANA BEACH — For many coastal residents who live alongside Interstate 5, the sound of tires hitting slabs of pavement and noisy air brakes on trucks is a daily annoyance. Which is why more than 100 people packed into the Solana Beach Community Center on Jan. 11 for a presentation on the latest efforts in freeway noise reduction.

The event, which was sponsored by the Solana Beach Civic & Historical Society, included Solana Beach Mayor Joe Kellejian, Solana Beach Deputy Mayor Dave Roberts and Encinitas Deputy Mayor Maggie Houlihan. Allan Kosup of Caltrans was also on hand as well as Doug Carlson, executive director of the Rubber Pavement Association, who flew in from Tempe, Ariz., to talk about a type of quieter road surface.

Plans are currently under way for a major facelift to a 30-mile North County stretch of Interstate 5 known as the Interstate 5 North Coast Corridor Project. The proposed project would involve adding two lanes in each direction from La Jolla Village Drive all the way to Oceanside.

Kosup said more than 220,000 people commute past Solana Beach on Interstate 5 each day, a number that is only going to increase over the next 10 years.

“This freeway has done its time,” Kosup said. “It’s done about 40 years. We need to look at it and say ‘What are we going to do for the next 40 years, knowing that we need to serve these people.’”

Also in the works is the extension of the existing carpool lane heading north. The lane, which currently begins in Sorrento Valley and ends at Manchester Drive, will be extended to just past Manchester Drive.

Work is also under way on the Lomas Santa Fe Drive/Interstate 5 interchange in Solana Beach. Direct on/off-ramps are being constructed to eliminate the need for waiting at a stoplight to turn left onto the freeway, which has been a cause for troublesome congestion during rush hour.

“We hope to be done in another 12 months from now with both the interchange improvements and the HOV lane extension,” Kosup said, noting the cost of those projects is approximately $60 million.

Kosup said one of the biggest challenges faced by freeway projects is dealing with the noise generated by the wheels of cars and the large air brakes on semi trucks.

“The traditional ways of mitigating noise are sound walls and sound berms, and those will be a component of this project,” he said.

But he added that walls have their downsides — they only mitigate for ground level noise, not for noise that rises above the freeway, plus they can be unsightly.

“We also don’t want to be like Los Angeles with an entire corridor of 30-foot walls,” Kosup said. “We don’t want to block coastal views.”

A solution might be Rubberized Hot Mix Asphalt, a breed of quieter road surface that would be laid over the freeway’s existing Portland Concrete Cement, or PCC.

Doug Carlson said the surface material was invented in Phoenix, Ariz., in the 1960s and is now the routine surface material for 85 percent of the roads in the state.

The process for Rubberized Hot Mix Asphalt begins with an old recycled tire. The tire is chopped until it resembles ground coffee and then it is boiled into a hot mix, which is laid over an existing surface. The material uses approximately 1,000 tires per lane, per mile.

Carlson said that regular PCC generates about 95 decibels of road noise as compared to 92 decibels for Rubberized Hot Mix Asphalt.

That may not sound like a big difference on paper, but he said it would be a noticeable improvement for surrounding homes.

“The difference in sound is about the same as if you doubled your distance from the noise source,” Carlson said.

Carlson said the surface material also enhances safety by increasing the skid resistance of tires and the surface is semi-permeable, allowing water to trickle down through the grains, which reduces the amount of splashing from tires during inclement weather.

The biggest issues, according to Kosup, with using Rubberized Hot Mix Asphalt are long-term maintenance and funding. The surface material lasts about 10 to 15 years on average.

“We’d be looking at about $30 million for each time we go through the corridor to redo the rubberized surface,” he said. “Right now the commitment isn’t there at the state level to find a way to make that happen.”

Roberts is optimistic that the needs of Interstate 5 can be met without sacrificing the quality of life for Solana Beach residents. “We will continue to actively seek funding,” he said.