Fillmore • Interstate 15 express lanes are not exactly express-like lately. Average speeds have dropped to just 31 mph during peak drive times in Salt Lake County, in part because so many toll-paying drivers are crowding into them.

So the Utah Department of Transportation is proposing to double the flexible tolls — upping the $1 maximum per section charge to $2, depending on congestion at the time.

However, members of the Utah Transportation Commission — which received the proposal Friday — said that increase may not be enough to significantly cut express-lane congestion. So members suggested raising it even more, perhaps to $3 or higher, and implementing it in stages to see how different toll levels affect traffic.

The commission plans to take public comment on the matter for at least a month. Whatever the commission recommends will be forwarded to the Legislature, which will make a final decision on the fees.

“The goal of the express lane is to encourage people to carpool, to double up and get in that lane,” said Rob Clayton, UDOT director of traffic management. “The goal is to maintain 55 mph in that lane, so people see that and have an incentive to carpool.”

But UDOT also has allowed single-occupant cars willing to pay tolls — plus some clean-fuel vehicles that buy “C decals” — to use extra capacity that had existed in those lanes. Trouble is, too many people are now using them.

“The volumes have risen to the point that the speeds are significantly deteriorated. So we have to look at ways to decrease that volume,” Clayton said. That now includes doubling the tolls paid by the 20,000 cars that now have transponders for electronic payment of tolls.

“There are too many people willing to pay that [$1 maximum] toll for it to act as a control” to decrease crowding, Clayton said.

Meg Holbrook, a member of the Transportation Commission, said, “I’m not sure that $2 is enough” to reduce congestion, and suggested going perhaps to $3. Commission Chairman Kent Millington said he would not oppose even higher tolls to allow testing public response.

A $3 toll or more would drive him out of express lanes, said commissioner Wayne Barlow.

UDOT Executive Director Carlos Braceras said his agency will refine proposals more, and perhaps come up with a plan on how to raise tolls incrementally until it finds a level that will cut congestion to desired levels.

“We’re not trying to make money” with higher tolls, Braceras said. “We just trying to move as many people as possible.” UDOT has said its toll program essentially just covers the cost of its transponder program, plus brings in some money to maintain express lanes.

Clayton used plenty of graphs and data on Friday to show how slow express lanes have become.

Every afternoon in Salt Lake County between 1300 South and the Utah County line, speeds start to drop below the 55 mph goal by about 4 p.m. They bottom out at 31 mph on average by 5:15 p.m. and don’t rebound past 55 mph again until nearly 6:30 p.m.

Congestion also occurs in the morning drive time, but is not quite as bad, Clayton said. Also, while traffic-clogged express lanes are worst in Salt Lake County, spots can also be bad in Davis and Utah counties.

Tolls are now about 10 cents per mile on average, and would double to 20 cents. Clayton said that is far less than the toll per mile charged in other Western states, which he pegged at an average 87 cents a mile. Some examples ranged from a low of 43 cents a mile on Interstate 880 in California to $1.10 a mile on California’s Interstates 10 and 110.

UDOT spokesman John Gleason said raising tolls is just one of many steps that UDOT has taken or plans to take to try to reduce crowding in express lanes.

For example, it has placed a cap of 6,650 “C decals” for purchase to allow clean-fuel, single-passenger cars into the express lanes. UDOT has already hit that limit — and has a waiting list of 1,065 people hoping to buy a C decal someday if current holders sell their cars or decide not to renew them.

A big problem is motorists who drive in the carpool/express lanes illegally. Past studies by UDOT consistently found that about one of every five cars there were violators.

UDOT will continue to fund occasional blitzes by the Utah Highway Patrol to specifically target and ticket violators, Gleason said. The Highway Patrol has said in the past that while it attempts to enforce that law, it sometimes takes a back seat to more pressing needs such as handling accidents or enforcing speeding.