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(Steve Griffin | The Salt Lake Tribune) Arrows point to the direction of traffic on first-of-their-kind-in-Utah 'flex lanes' on 5400 south in Taylorsville. State highway and police records indicate the experimental reversible lanes are as safe — perhaps even more safe — than regular, static lanes.
‘Flex lanes’ aid traffic flow — and are proving safe
Traffic » Stretch of reversible-lanes on 5400 South shows improved flow and, so far, fewer crashes.
First Published Jul 08 2013 01:01 am • Last Updated Jul 08 2013 04:43 pm

New reversible "flex lanes" on 5400 South in Taylorsville — where some lanes go one direction in the morning and the opposite way in the afternoon — are carrying more traffic more quickly than before the conversion. And to the surprise of many, they haven’t increased crashes.

"We get calls from people who say they won’t drive there anymore because it scares them or they feel it is dangerous. But the data show something different," says Utah Department of Transportation spokesman Adan Carrillo.

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For a 1.9-mile stretch between 1900 West and Bangerter Highway, the road has four lanes of traffic in the direction of heavy commuting at peak times and two in the other direction — plus a turning lane. At off-peak times, it allows three lanes in each direction. They are the state’s first reversible lanes, built to avoid widening the road and demolishing many businesses and homes.

Travel data » A UDOT-commissioned study by Avenue Consultants shows that in peak directions, the road is carrying 17 percent to 21 percent more traffic — depending on the time of day and where traffic is measured. That amounts to 290 to 380 extra cars per hour.

While carrying that extra traffic — some of it apparently switching over from busy 4700 South — the study said afternoon peak-direction travel times were reduced by 50 seconds ­— thanks to the extra lane. Travel time dropped by 45 seconds during the morning commute.

Meanwhile, in the off-peak direction, traffic volume remained essentially the same, depending on the spot measured.

Afternoon off-peak travel times were reduced by 20 seconds — even though a lane was lost in that direction. But morning off-peak travel times increased by 65 seconds.

The study said the benefits of shorter travel times in peak directions with higher volume "outweigh the detriments of the increased travel time in the a.m. nonpeak direction."

Information for the study was collected in April and compared to travel data for May 2012. The flex lanes were activated in November.

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Accidents » While rush-hour commutes have been eased a bit, safety concerns voiced when the new system came on line haven’t materialized, according to preliminary data provided by UDOT and the Unified Police Department.

From the time the lanes were activated in November through May, UPD numbers show 34 accidents in the flex-lane area. That is down from 54, 53 and 77 during the same period and place during the three preceding years, according to UDOT data.

Robert Miles, UDOT traffic operations engineer, cautions that data for the most recent period are considered preliminary and not verified. He also noted that accident information sometimes is not put into databases immediately by police.

"I’m not willing to say at this point that flex lanes made it safer," Miles said. "But it [the information] tells me we haven’t made it worse."

The preliminary data did not include whether any of the 34 accidents reported were head-on, although Miles said UDOT was not aware of any fatalities on the stretch. In the three years before conversion to flex lanes, that stretch of road had five head-on collisions, 54 crashes with injuries but no fatalities in similar November-May periods that were examined.

Unified police Lt. Justin Hoyal said because the numbers at first looked surprisingly low, he had his department run them again a little differently — between Redwood Road and Bangerter [where cars could be confused as they approach flex lanes] for January through June comparing 2012 and 2013.

In 2012, that area had 122 accidents, compared with 101 this year (although not all accidents in June may yet have been counted).

"Even with these flex lanes, the number of crashes are about the same or less," Hoyal said.

Miles said another measure that suggests accidents are not out of line in the flex-lane stretch is comparing accidents there to other parts of 5400 South.

For November through May, the flex-lane area had 17.9 accidents per mile. Other portions of 5400 South between 1400 West and State Road 111 (at the base of the Oquirrh Mountains) had 21.6 accidents per mile.

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