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The Monday Morning Commute: Ask the traffic engineer: Scottsdale seems to have more right-turn arrows than any other city. Why?

Posted by   /  July 6, 2020  /  No Comments

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By Paul Basha, traffic engineer, Summit Land Management

Correct. In the late 1980’s, Scottsdale installed right-turn arrows for exclusive right-turn lanes at almost all of its major intersections. And their practice continues.

Prior to the construction of the Pima Freeway in the late 1990’s; Scottsdale Road, Hayden Road, and Pima Road were the only north-south streets in Scottsdale. So, Scottsdale drivers turned between east-west and north-south streets in greater concentration than drivers in cities with grid street systems like Phoenix and Mesa. Therefore, Scottsdale needed to be more creative than other cities.

Compared to left-turn traffic, right-turn traffic moves quite freely, and therefore most traffic engineers do not worry much about right-turns. They need to focus their attention on the problems: left-turns. (Scottsdale did that as well, hence the lagging left-turn arrows, both safer and more efficient for all traffic.)

Right-turns have low delay, right-turn arrows do not reduce high delay to low delay.

However, right-turn arrows are convenient. Simply makes sense that when green left-turn arrows appear, compatible green rightturn arrows should also appear. It eliminates the stutter stop necessary for a right-turn-on-red. As with everything traffic – every good idea has a bad side. So, the eastbound rightturn can have a green arrow with the northbound left-turn.

Not with the northbound-tosouthbound u-turn. The attorneys advising the traffic engineers stated the obvious: a green arrow tells drivers that everyone else has a red light. An eastbound-to-southbound right-turn car would badly surprise a northbound-tosouthbound-u-turn driver if both had green arrows. So, compared to other cities, Scottsdale has more green right-turn arrows, and also more no u-turn signs.

Curious about something traffic? Call or e-mail Paul at (480) 505-3931 and pbasha@summitlandmgmt.com.

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  • Published: 1 month ago on July 6, 2020
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  • Last Modified: July 6, 2020 @ 10:07 am
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