2. UDOT News

Thru with Delay

An intersection type that was new to Utah reduced delay and improve safety through a busy Draper business district.

Utah’s first ThrU-Turn Intersection was built at 12300 South and State Street. UDOT adapted a Michigan U-Turn, commonly built from scratch in the mid-west, in an innovative retrofit improvement that upgraded the safety and function of the busy intersection. The TTI provided 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 caused congestion and concern. Future traffic demand projections showed that by 2030, crippling delay would cause traffic to spill onto surrounding streets. Without improvement, motorists would eventually avoid the area altogether or just pass through as a commuter – not good news for an urban business center.

The TTI was an excellent solution to future congestion that came with an impressive cost-benefit analysis. The budget was relatively small at just under $5 million. During the first year of operation, road users saved 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 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 travel out-of-direction for a short distance, traffic modeling shows that left turn travel times are reduced. “People make U-turns all the time when intersections are too busy…here it’s engineered for safety, efficiency and convenience,” said 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 reduces 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 also improves safety. The TTI design lets motorists move safely around medians to access business. Since traffic congestion was reduced, motorists coming from the freeway 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 focused on teaching the public how to drive the TTI. Law enforcement was on board too – during the first few days of operation, police officers handed 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 reduced delay, and the minimal widening areas needed are away from the intersection where utilities and signal poles weren’t disturbed.

One great way to reduce inconvenience to business and road users is to limit project duration. Construction for the TTI was quick and easy because the project required minor road widening, new signals and striping. Just a few months of minimal impacts delivered better traffic flow.

*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.

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