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Roger Lewis: Roundabout economics

Posted: May 16, 2014 - 4:47pm

The joke is that everybody complains about the weather but nobody does anything about it. In Conway everybody complained about the traffic but ... well, in Conway something HAS been done.

The Problem

The problem is increased traffic: delays, accidents and expense. Passenger vehicle registrations increase in Faulkner County an average of 2,500/year. In 2000 the number of registrations was not quite 65,000. In 2013 the number was 97,500, a 50 percent increase. This trend puts us at 130,000 by 2025. Will we build enough roads or additional lanes to handle this increase? Probably not, but there is help for the problem.

A Solution: Roundabouts

The first roundabout in Conway (2004) was at the intersection of Washington, Tyler and Winfield. Often referred to as malfunction junction, two unaligned streets, Tyler and Winfield intersect Washington. The signal system was elaborate, expensive and held up traffic inordinately as it cycled through. Conway’s first roundabout eliminated all signals, was very successful, and sold the public on the concept.

The second and third roundabouts were then built on Harkrider, the major highway through Conway. I was skeptical when these were proposed; I didn’t think they could handle the high volume of traffic. However, they work wonderfully with the high traffic counts. The Arkansas Department of Transportation and Highways reported of average of 28,000 vehicles per day on Harkrider in 2013.

Prince Street now has four roundabouts with an average traffic count of 15,000 vehicles per day. Traffic is moving more swiftly through this corridor, not because vehicles are moving at a higher rate of speed but because waiting time at intersections is reduced by 75 percent, according to the city’s traffic engineer.

Features of Roundabouts

Safety. Roundabouts reduce both the number of accidents and their severity. While the amount of traffic on roundabout streets has increased each year, the number of accidents has not. The two-year average before and after for the two roundabouts on Harkrider (excluding the year of construction) shows an average of 20 accidents before and 20 accidents after.

The Conway Police Department rates accidents for severity. Since the above roundabouts have been completed, nearly all the accidents were rated 5, property damage only, or 4, possible injury. None of the accidents have been 1s or 2s, fatality or incapacitating injury. Only two accidents were category 3, non-incapacitating injury. One must conclude that roundabouts are a safer way to move traffic.

Delays. Roundabouts move traffic more swiftly, which is a surprise because they slow down traffic. A camcorder suspended over Prince Street from Donaghey to Salem would show that before the roundabouts, the traffic moved in waves with nodes at each traffic signal.

Traffic would consolidate at traffic signals and then spread out in the space between signals. With the roundabouts, the traffic flow is smoother, greatly reducing these nodes of bunched-up traffic at intersections.

Economics. Roundabouts are more economical for both motorists and the city of Conway. Waiting time is reduced by about 75 percent at roundabout intersections, compared to an intersection with a traffic signal, so cars set at idle for less time, using less gasoline and saving motorists money. Here is a “back of an envelope” approximation. Fifteen thousand cars traverse Prince Street each day through four roundabouts. If the roundabouts reduce idling time on average one minute 15,000 cars means 15,000 minutes or 250 hours each day that cars are not stopped with the motor running. The Automobile Association of America states that a car idling for one hour consumes one gallon of gas.

Thus, each day 250 fewer gallons of gas are consumed because of these four roundabouts. Gasoline at $3 per gallon (hopefully once again) means a saving for motorists of $750 per day. This equates to $273,750 per year, an astonishing figure. But there’s more. Signals require complete stops but roundabouts mostly require slowing down. Acceleration from stop consumes considerably more gasoline than acceleration from slow. Finally, considering all 11 roundabouts in Conway, plus the acceleration issue, we are talking about millions of dollars saved in gasoline consumption in Conway each year because of roundabouts.

Less gasoline equals less pollution, a benefit to our environment. In addition to motorists saving money, the city of Conway does too by not purchasing nor maintaining traffic signals. So, Conway roundabouts save motorists and the city millions of dollars each year.

Roundabouts work. They are safer, move traffic faster and reduce costs. There are more to come.

I thank my friend Chris Spatz for editing and helping with this article. More information on Conway’s economy can be found at www.pulseofconway.com

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