Motorists in Round Rock are undergoing a transition in how they manage left turns.

On Nov. 13, the city began converting the left-turn signals along some of its busiest corridors. The new systems, which add a flashing yellow arrow to the existing green, yellow and red arrow signals already in place, were first installed along University Boulevard and have since expanded to Gattis School Road.

The changes, which were done in compliance with new federal and state standards for left-turn signals, are designed to eliminate confusion as to the meaning of left-turn signals, according to the Texas Department of Transportation. Round Rock transportation officials, however, admit the new system will take some time and experience for motorists to adjust to.

"There is no question there is a bit of a learning curve," Round Rock Transportation Director Gary Hudder said. "But I have seen over the last weeks an improved understanding. At this point I would say I'm a believer."

The flashing yellow arrows act as a replacement left-turn signal to the green circle light, which according to TxDOT was commonly confused to mean a protected left turn. When drivers are given a flashing yellow arrow signal, it indicates that left turns are allowed, but that motorists should yield to oncoming traffic and pedestrians in walkways. The remaining light signals act as they did prior to the change. A steady green arrow indicates a protected turn, a steady red arrow indicates stopping and a steady yellow arrow means drivers should prepare to stop.

"The No. 1 benefit is improved safety," TxDOT spokeswoman Kelli Reyna said. "People already have it ingrained in their mind that yellow means slow down or stop, so it is helping them to be more cautious."

Hudder said one benefit of the new system is improved traffic flow. The new system allows traffic systems to display the flashing yellow lights when in the past the lights would have remained red. The result is an increase in the amount of cars turning left during the average light cycle.

"We have seen up to a 30 percent improvement in left-turn through traffic," Hudder said.

According to evidence collected by another Texas city that has been running the flashing yellow arrow system, the greatest benefit may be to traffic flow, not drivers' safety.

The City of Waco began installing the flashing yellow arrow systems in June 2010, soon after the new federal mandates were released. The city is currently studying the effect of the light systems and has noticed an increase in accidents at several of the intersections since the change, said Colin Taylor, a City of Waco traffic analyst.

"Whenever you change a signal system, it is something that people take some time to get used to," Taylor said.

The City of Waco's Transportation Department released a study one year after the installation of its first flashing yellow arrow signals that found a slight increase in the number of accidents but a decrease in travel time along some corridors.

"While the safety for some approaches ... [has] not improved due to the allowance of permissive left-turns ... the amount of delays, stops and consumption of fuel has been greatly reduced due to this implementation," the report stated.

The new systems are only required in newly constructed intersections. Round Rock's Transportation Department, however, decided to integrate the system onto some of its busiest roads to coincide with the retiming of its light signals. Hudder said the city already has plans to add the flashing yellow lights to intersections along Old Settlers Boulevard and is also planning to include signals along Hwy. 79 and RM 620 in the near future.

Hudder said the conversion to the new system will cost the city an average of $1,500–$2,000 per intersection, paid from the city's existing traffic signal budget.

"This is a pretty intricate process," Hudder said about the light conversions. "It does require different [signal] hardware and sometimes computer software as well."