Roundabouts not practical for traffic on 89A
The Arizona Department of Transportation is proposing to install two roundabouts, one at the junction of 89A, Cement Plant Road and 11th Street in Clarkdale, and another at the junction of an access road to Centerville and 89A. This is part of the Mountain Gate development.
It was also proposed at a recent meeting of the Clarkdale Planning and Zoning Commission that another roundabout be installed at the junction of an access road to the Mountain Gate Development and 11th Street.
The theory of roundabouts, I believe, is that to negotiate an intersection traffic does not have to stop, but merely slow down. However, I have heard it stated that traffic flow is not significantly improved over traffic lights.
I have driven an automobile in the United Kingdom and most of Europe for nearly 20 years, and in the United States, Canada and Mexico for over 35 years. Roundabouts are also known as rotaries or traffic circles in different parts of the world. I have encountered various types, large, small, single and multi-lane, plain and landscaped. Their only redeeming value so far as I can determine is that they generate markedly improved business to the local body shops.
Here's why. In what might be called "normal" conditions, roundabouts work just fine.
There is sufficient space in the circling traffic to allow vehicles to enter the roundabout without stopping. However, when the traffic gets heavier, vehicles approaching the roundabout cannot find space on the circle to enter. They have to stop, and this is where the problem is. There is no acceleration lane for vehicles to merge safely. They have to wait for a sufficiently large gap to enter the circle. This may take a few seconds or a few minutes. Meanwhile more traffic piles up at the roundabout entrance.
To compound the problem, the paths of vehicles trying to enter cross the paths of vehicles trying to exit to their right.
Imagine this scenario. A cement truck on the Cement Plant Road arrives at the roundabout on 89a and 11th street and traffic is heavy. The driver needs to continue along 89A toward Cottonwood. While the driver waits for a gap to enter the circle, another cement truck arrives behind it. Finally, the driver of the first truck sees an opening so he starts forward.
Cement trucks are not known for their blazing acceleration, so traffic on the circle slows and stops, blocking all the entrances. The second cement truck driver sees the problems the first driver had in gaining access to the circle, so he follows right behind the first truck, prohibiting the circle traffic to move. Traffic now piles up at all the entrances and may take as long as 10 minutes for the roundabout to achieve a normal function after the cement trucks have passed.
I don't know if there is anything that can be done to change ADOT's mind about roundabouts in Clarkdale, but we can certainly raise our voices at Clarkdale Planning and Zoning Commission, and Council meetings to express our opposition to the roundabout proposed at 11th Street and the access road to Mountain Gate.