A Roundabout Approach to Reliability


R U N N I N G   R E L I A B LY


Traveling outside the US routinely provides me with the opportunity to see and learn how other countries and cultures achieve reliability. Because reliability revolves around the ability of both people and objects to function well for a desired time under specified conditions (the end use environment), it can mean quite different things in different places. A recent trip to New Zealand educated me on a couple of items I’d long wondered about: driving on the left hand side of the road and roundabouts. And, since New Zealand is one of the most geologically active areas in the world, environmental factors would seem to play a major role in reliability.

One thing I quickly noticed while driving on the opposite side of the road (and from the opposite side of the vehicle) was that my Mazda 3 had transposed the location of the levers for the turn signals and the windshield wipers. All other controls, including the gas and brake, were in approximately the same relative location as in my US vehicle; but, as I later learned, the location of the turn signal and wiper levers in New Zealand vehicles varies by whether the manufacturer is Asian or European. I found this to be a rather risky practice. Why shouldn’t location of critical controls be standard in vehicles or at least standard within a given country? Aircraft manufacturers seemed to have learned this lesson and arrange flight instruments in standardized patterns. No fumbling to find the right controls there! For me, this non-standard practice resulted in more than a few instances of inadvertently turning on the wipers rather than signaling a turn – a rather disconcerting experience and one not appreciated by my fellow drivers. With this small, unexpected change in design, I became an unreliable driver even though I had quickly adapted to driving on the left side! The photos below show me as I navigated and adapted to my new driving circumstances.

Figure 1. Driving in New Zealand.

With its steep mountains and hillsides of soft rock, New Zealand is prone to landslides. Combine that with earthquakes and years of rocks weakened by them and you’ll find a challenging landscape for maintaining roadways. In the major November 2016 7.5 earthquake event alone, more than 313 smaller quakes and over 100,000 landslides were reported with the disruptions stranding some people for days.1 Considering the environmental challenges New Zealand faces, however, I was quite impressed with the condition and maintenance of the roads there. Although we encountered numerous areas where the highway was reduced to a single lane, traffic flowed smoothly, road markings were clear, and crews were quickly making repairs to roads. We never faced a delay of more than 10 minutes during our entire 1014 miles of driving. When roads went down to a single lane total, New Zealand often used nifty portable traffic lights2 which eliminated the need for people to manage traffic. These were used only in areas where the one lane was a temporary event due to weather damage.

Where the one lane was a permanent fixture due to narrow bridges, the situation was marked with a give way sign indicating who had right of way. A red arrow indicated the direction which needed to yield to oncoming traffic.

These portable lights combined with the relatively small number of signalized intersections and frequent road maintenance seemed to provide robust, reliable traffic management on New Zealand roadways.

I was fascinated by the significant use of roundabouts throughout the country for both minor and major interchanges. Statistically, modern roundabouts are safer for drivers and pedestrians than both traffic circles and traditional intersections.3 For many situations, they are faster as well. Studies of roundabouts that replaced stop signs and/or traffic signals found that vehicle delays were reduced 13–89 percent and the proportion of vehicles that stopped was reduced 14–56 percent. Delays on major approaches did increase as vehicles slowed to enter the roundabouts so they’re not as well-suited for high volume intersections.4 Roundabouts also reduce costs significantly through lower annual maintenance and life-cycle replacement costs, lower crash costs and reductions in delays and decrease in air pollution and fuel use.5

However, what I found more compelling was the potential reliability benefits of roundabouts. Traffic signals cost money to install, maintain and operate and are vulnerable to weather-related disruptions from hazards like wind, trees, power outages, and even bright sunlight. Earthquakes and landslides are further challenges in New Zealand as well as in areas of the United Sates. With these potential advantages, why don’t we use them more in the US? Simply re-timing an existing intersection signal costs a surprising amount of money. The National Traffic Signal Report Card reports costs to update signal timing of up to $3,000 per intersection.6 In addition to the initial construction costs, ongoing maintenance costs are generally higher for a signalized intersection than the cost of maintaining a roundabout. “Where long-term costs are considered, roundabouts eliminate hardware, maintenance and electrical costs associated with traffic signals, which can cost between $5,000 and $10,000 per year.”5 Combined with the fact that roundabouts reduce injury crashes by 75 percent compared with signalized intersections and reduce traffic fatalities by 90 percent compared with signalized intersections makes them look even more compelling.7 When considering the number of traffic signals in a typical US city, those benefits quickly add up.

New Zealand has definitely identified solutions for optimizing traffic reliability for their unique environment. Their solutions ranged from low tech (signs) to high tech (portable traffic lights) to alternative tech (roundabouts versus signalized intersections) combined with ongoing maintenance – a truly comprehensive approach. Would the US benefit from wider use of some of New Zealand’s road practices? I think so!


1. https://www.theguardian.com/world/live/2016/nov/15/new-zealand-earthquake-floods-wellington-kaikoura

2. http://www.rtl.co.nz/c/Portable-Traffic- Lights/p/709/RTL-MPB-4000-Portable- Traffic-Lights.aspx

3. Shashi S. Nambisan; Venu Parimi (March 2007). “A Comparative Evaluation of the Safety Performance of Roundabouts and Traditional Intersection Controls”. Institute of Transportation Engineers.

4. http://www.iihs.org/iihs/topics/t/ roundabouts/qanda

5. http://www.heraldtribune.com/news/20090621/a-traffic-circle-and-a-roundabout-are-not-the-same

6. http://www.itscosts.its.dot.gov/its/benecost.nsf/0/215F723DB93D293C8525725F00786FD8

7. http://pugetsoundblogs.com/roadwarrior/2012/09/25/comparing-costs-of-roundabouts-and-traffic-signals/



Cheryl is a reliability engineering consultant with over 20 years of experience in electronics manufacturing focusing on failure analysis and reliability.


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