Flashing arrows should make left turns safer

You might have seen the new traffic signals that the city of Las Vegas installed on Tuesday. Or you might not, because they are only located at two intersections at this point. But it is worth explaining how they work in case you encounter them. With the help of city traffic engineer O.C. White, this column is dedicated to anticipated questions about the new amber turn arrow.

OK, what the heck are you talking about?

These new traffic signals were turned on Tuesday at the intersections of Alta and Town Center drives and at Smoke Ranch Road and Decatur Boulevard. What you will see when you approach the intersection is a long signal box housing four lights -- a green arrow, a yellow arrow, a flashing yellow arrow and a red arrow.

How does it work?

The only light that we hadn't seen before is the flashing yellow arrow. This replaces the green ball that allowed motorists to make a left turn when there was a gap in oncoming traffic. It serves the same purpose as the green ball. Drivers who pull up to a flashing yellow arrow can pull into the intersection and cautiously make the turn, yielding to oncoming traffic. The solid yellow arrow warns motorists that the light is about to turn red. The green arrow will still exist to clear the turn pockets. The yellow flashing arrow is activated when most of the through traffic has moved through the intersection.

If it serves the same purpose as the green ball, why make a change?

Not all motorists understood the green ball or didn't recognize right away that they were not free to turn. "Sometimes they think they have the right to go first," White said, explaining that the confusion results in some ugly accidents. "Yellow means caution. It's clear it's all right to make a turn, but you have to be cautious." So it is essentially the yellow is more effective in capturing the attention of drivers.

Is it proven that this is a safer system?

Traffic engineers in Seattle gave this a go in the early 2000s and found it to be largely successful. And studies have been conducted that show the signal is less confusing. "The idea was that it could be safer because you have a better idea of what to do when you get to the intersection," White said. "In most places it made the operation become a little smoother."

How do they decide where to put them?

They chose the intersection at Town Center and Alta because there were 24 accidents over a three-year period. They are targeting the more dangerous areas first. They also were installed at Smoke Ranch Road and Decatur Boulevard on Tuesday. The city, using funding from the Nevada Department of Transportation, hopes to install 300 more.

Where you will not see these lights are in intersections that have dual left-turn lanes. They also won't be placed in intersections where the view of oncoming traffic is impeded by a curve in the road or a steep grade. The city doesn't allow motorists to yield on such dangerous intersections because it is difficult to see or gauge the speed of oncoming traffic.

Will engineers use these flashing arrows during certain times of the day?

Yes, they will be activated most of the day, but it becomes more of a problem during rush hour. "During peak hours, you have people making decisions on whether the gap is big enough and cars get backed up in the turn lane," White said. So, instead of using the flashing amber signal, engineers will revert back to strictly using the green arrow so that motorists can proceed safely.

Will this mean that I no longer will sit forever at a red light at 5 a.m. when no oncoming traffic is in sight?

Hopefully this new technology will alleviate that problem. Many readers who work early or late have expressed frustration that they sit idling in a turn pocket for several minutes when there is hardly anybody else on the road. They even try backing up and moving forward to trigger the sensor. If the street on which you are traveling has the green light, the left-turn signal will be a flashing yellow during these times of day to let motorists continue on when there is no traffic.

In some cities, a major street is controlled by blinking amber lights allowing motorists to move through the intersection carefully while side streets have red blinking lights. Will we ever see that system here?

That is not likely to happen in Las Vegas. It's an efficient system in smaller, quieter communities but because our city is a 24-hour town with residents from all over the world, that type of signaled intersection would likely be too confusing and therefore not work well here.

Finally, how long do you think it will take motorists to get used to this flashing yellow arrow?

"That's a good question," White said.

Contact reporter Adrienne Packer at apacker@reviewjournal.com or 702-387-2904.