August 11th, 2011

THRU WITH DELAY

Optimize Mobility, by Catherine Higgins.

This post highlights UDOT’s ThrU-Turn intersection – want to know more about construction impacts? Attend the ThrU-Turn Open House on Monday, August 15 from 4 to 7 p.m. at Draper City Hall Council Chambers, 1020 East Pioneer Road (12400 South). Construction starts this week with completion scheduled for late 2011.  Project Hotline: 888-914-5454. Send an email to thrUturn@utah.gov for weekly updates.

An intersection type that’s new to Utah will soon reduce delay and improve safety through a busy Draper business district.

Utah’s first ThrU-Turn Intersection will be built at 12300 South and State Street. UDOT has adapted a Michigan U-Turn, commonly built from scratch in the mid-west, in an innovative retrofit improvement that will upgrade the safety and function of the busy intersection. The TTI will provide significant relief from traffic delay on the first day of operation and well past 20 years, according to UDOT traffic studies.

Wait-times at the intersection are causing congestion and concern. Future traffic demand projections show that by 2030, crippling delay will cause traffic to spill onto surrounding streets. Without improvement, motorists will eventually avoid the area altogether or just pass through as a commuter – not good news for an urban business center.

The TTI is an excellent solution to future congestion that comes with an impressive cost-benefit analysis. The budget is relatively small at just under $5 million. During the first year of operation, road users will save almost $1 million–a lot of user-cost savings for the money spent.*

The TTI re-routes left turns

Instead of turning left at the intersection, motorists will proceed through and make a U-turn at a designated turning point, wait briefly at a signal before going straight, then turn right. Turning areas are designed for commercial trucks, so vehicles will be able navigate easily. Even though left-turners will be traveling out-of-direction for a short distance, traffic modeling shows that left turn travel times will still be reduced. “People make U-turns all the time when intersections are too busy…here it’s engineered for safety, efficiency and convenience,” says Adan Carillo, Public Involvement Manager at UDOT Region Two.

More safety, less delay

Safety is top priority for UDOT. Moving left turns away from intersections will reduce the number and severity of crashes.

The TTI is close to freeway exits where traffic tends to weave, increasing the likelihood of crashes. Adding medians and improving traffic flow will also improve safety. The TTI design lets motorists move safely around medians to access business. Since traffic congestion will be reduced, motorists coming from the freeway will have more time and space to safely change lanes.

The TTI’s efficiency is all in the signal timing. Eliminating two protected left turn phases from the signal cycle improves efficiency by moving more traffic through the intersection. A two-phase signal cycle can easily be coordinated with signals, keeping traffic progressing through the rest of the corridor.

Driver friendly

UDOT has given a lot of time and thought to signs and lane markings in the area. The TTI logo shows the traffic path, and the signs are big enough to be seen easily but not so big as to be obtrusive. Lane markings also show the traffic path. Public information efforts will focus on teaching the public how to drive the TTI. Law enforcement is on board too – during the first few days of operation, police officers will hand out instructive flyers instead of citations when people break traffic rules.

The TTI is a cost effective solution that reduces delay while carefully considering the needs of the local community.

When investigating solutions, UDOT looked for a cost-effective way to improve traffic flow with minimal inconvenience to business owners. UDOT’s design team considered a CFI and some grade-separated alternatives; those options would have helped traffic but at a high cost to tax payers. The TTI effectively reduces delay, and the minimal widening areas needed are away from the intersection where utilities and signal poles won’t be disturbed.

One great way to reduce inconvenience to business and road users is to limit project duration. Construction for the TTI will be quick and easy because the project requires minor road widening, new signals and striping. Just a few months of minimal impacts will deliver better traffic flow by the end of the year.

*Savings to road users is calculated by identifying the average cost of delay to road users, then comparing delay reduction to a “do-nothing” scenario.

The Thru-Turn Project Team:

Peter Tang, Project Manager, UDOT

Marwan Farah, Resident Engineer, UDOT

Adan Carillo, Public Involvement Coordinator, UDOT

Mel Bodily, Traffic Engineer, Avenue Consultants

Dan Young, Project Manager, PEC

Marc Bennett, Design, PEC

April Gordon, Public Involvement Manager, Jacques and Associates

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    […] to Utah DOT’s Adan Carillo, the ThruTurn intersection in Draper, Utah, was a controversial solution to a congested and troubled commercial intersection near Interstate […]

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