Flashing Yellow Left Turn Arrows

In October 2008, Scottsdale’s Transportation Department installed a new type of traffic signal indication - a flashing yellow left turn arrow - at two intersections:

• Raintree Drive at Northsight Boulevard
• 68th Street at McDowell Road

Only the north and southbound left turn lanes at these two intersections will have the new signals.

Recent Data

Recent data collected at these two intersections show a significant reduction in left-turn collisions over the past two years.

• At the Raintree Drive and Northsight Boulevard intersection, traffic collisions declined from five a year, prior to the installation of the flashing left-turn signals, to one collision a year after installation – a drop of about 80 percent.
• At the 68th Street and McDowell Road intersection, traffic collisions declined from six a year, prior to the installation of the flashing left-turn signals, to one collision a year after installation -- an 83 percent drop.

Additional signals are being planned along Pima Road at Indian Bend Road and Via de Ventura.

Goals

The goal of the new signals is to improve safety at these intersections. Scottsdale is one of the first cities in Arizona to use these types of signals. These signals use a flashing yellow arrow to notify drivers turning left that they must yield to oncoming traffic and pedestrians before turning left.

Here what the new signals will look like and how they work:

• Steady red arrow = Stop (No left turns allowed)
• Steady yellow arrow = Prepare to stop
• Flashing yellow arrow = Left turns allowed, but must yield to oncoming traffic
• Steady green arrow = Left turns allowed

Left-turn Arrows

The flashing yellow arrow traffic signals consist of four arrow lights that are used exclusively for left-turning traffic. The arrow traffic signals are separate from the traffic signals containing circular lights for through traffic.

Benefits of New Left-turn Arrows

• Enables the left-turn control to be varied during the day.
• Eliminates motorist confusion as to the meaning of the circular green light, which can be mistaken as a protected left turn, and the simultaneous circular red light and green arrow (some motorists stop).
• Can be used in all intersection and signal configurations.
• Provides more opportunities for drivers to turn left.
• Can also be used for right turns.

The use of flashing yellow left-turn signals is the result of extensive research sponsored by the National Cooperative Highway Research Program. The research showed the flashing left-turn arrow was the most easily understood indication for drivers and is widely accepted in the traffic engineering industry.