On 7 August 1974, a 24-year-old French man named Philippe Petit performed one of the most daring and celebrated balancing acts of all time. Using a custom made 26 foot (eight m) long, 55 pound (25 kg) balancing pole, Petit performed a high wire balancing act between the Twin Towers of the World Trade Center in New York City. Petit performed 1,350 feet (400 m) above the ground for 45 minutes while a cheering crowd of office workers, police officers and school children looked on.
While the incredible height of the feat was cause for much of the celebration, the fundamental skill of high-wire walking is the same regardless of how far off the ground you are: balance.
Traffic engineers may never be as celebrated as Petit and road construction projects may never bring the cheering crowds of what Petit called “le coup”, but engineering a safe and efficient highway is still a balancing act that influences nearly every facet of life.
The “balance” traffic engineers often face refers to bringing harmony to two forces that seem to be in direct conflict. Cofiroute, a concessionary company for VINCI Autorotures, faced one such dilemma recently: how can you balance bringing innovative technology for modern intelligent transportation systems while protecting yourself from the risk of unproven technology? Just like Petit relied on his custom-made balancing pole, so, too, did Cofiroute rely on a tool to find the balance they required: the Wavetronix SmartSensor HD.
VINCI Autoroutes designs, contracts, finances, operates and oversees more than two million clients a day on its 2,725 miles (4,386 km) of highways in France. Cofiroute is the second largest concessionary company under VINCI with a network of 753 miles (1,211 km) in operation covering Paris, Poitiers and Nantes.
For close to 20 years, the Cofiroute network used data collection stations (DCS) to detect traffic. These systems relied on intrusive inductive loop technology to operate – a technology that is proven in terms of accuracy but problematic in other ways, especially when it comes to installation and maintenance.
Loops are difficult and dangerous to install. They must be saw-cut into the road surface, an act that requires lane closures and places road workers at risk. This danger multiplies when the high failure rate of loops is taken into account; loop arrays have multiple failure points and most all roadwork requires a completely new array installed, meaning workers must spend more time in harm’s way.
The high failure rate of loops brings another problem, that of gaps in data. With a goal of continually offering more services to its clients, such as travel times, speed regulations to improve traffic flow, incident detection and other applications, detection simply can’t fail.
“Traffic detection stations are an essential element for any ITS system,” says David Criaud, head of the Cofiroute Network Equipment Maintenance and Renewal Department of VINCI Autoroutes.
Facing these problems, VINCI took a hard look at the Cofiroute network to reduce traffic data downtime. The result was a decision to replace inductive loops with new detection technology that had to live up to very high and specific standards. The new technology had to be as accurate as loops while being more cost-effective and non-intrusive. The technology would also have to be proven through rigorous testing.
After considering many different forms of detection technology, VINCI decided to focus their efforts on the SmartSensor HD. This initial selection, based on the reports of previous studies, was only the first step for VINCI – investment in new technology can be risky if the technology doesn’t perform as anticipated.
“A responsible and rigorous approach across defined test protocols must be followed before validating any deployment of new metering devices,” Criaud says.
SmartSensor HD’s high definition, non-intrusive radar provides an entire suite of data, including traffic flow, lane occupation, vehicle classification, traffic direction, 85th percentile speed, and both average and per vehicle speed. Because it utilizes a dual radar beam system it mimics speed traps created by inductive loops.
Before testing could begin on HD, it had to integrate into the French MIVISU system, a feat that was accomplished by cooperation between Wavetronix and LABOCOM.
The testing period for HD was spread over one year at three test sites: an eight-lane highway near Ponthévard; a six-lane highway near Orléans; and a four-lane highway near Tours. The test compared data in real time, six-minute intervals between a perfectly calibrated inductive loop station and SmartSensor HD. Testing occurred day and night in a variety of weather conditions including wind, rain, snow and fog; and in a variety of traffic conditions, including free-flowing and saturated conditions. The test looked at how accurately HD measured the overall flow of traffic, the flow for heavy vehicles, average vehicle speed and occupation rates.
The results of the test were conclusive. For all three sites the average overall flow measurements saw an error rate of just .6 percent, far better than the three percent required by Standard Class B. The flow for heavy vehicles responded with an average error rate of 1.93 percent, better than the 10 percent Class B error rate threshold. The average error rate for average speed was .9 percent, again far better than the Class B standard of four percent.
Occupation rates were more difficult to compare because loops and HD utilize significantly different algorithms. However, HD was found to respond to traffic fluctuations similarly to loops.
The test concluded that variable weather and traffic intensity conditions did not generate notable variations when compared to normal testing conditions at all three sites.
The tests also highlighted additional advantages HD has over loops. “When comparing same services, the radar station is cheaper than the loop station,” says Michael Pépin, the Road Equipment Mission Manager at VINCI Autoroutes.
“When comparing same services, the radar station is cheaper than the loop station.” — Michael Pépin, Road Equipment Mission Manager at VINCI Autoroutes
Pépin’s point to the affordability of HD over loops comes from the non-intrusive nature of radar traffic sensors. Installation usually takes one or two workers around an hour on the side of the road when compared to the extensive work required to saw into the pavement to install loops. HD also wins the affordability game when it comes to equipment maintainability. HD easily outlasts several loop lifecycles without concern to environmental or road surface issues. Pépin also points out HD’s adaptability. Because it’s installed on a tilt-up tower, it can easily be moved or reconfigured to respond to new roadway configurations.
Proven accuracy, ease of installation, low maintenance, reduction of on-road equipment, strong adaptability and interoperability with MIVISU operating software were all important points that contributed to VINCI’s decision to utilize HD on the Cofiroute network. But Pépin and Criaud’s responsibility to balance the need to modernize vehicle detection and the need to protect the Cofiroute network from faulty equipment kept them vigilant.
“SmartSensor HD has several advantages, but one of its weak points is our lack of visibility on the technology’s behavior over the long term,” Pépin says.
Simply put, VINCI wanted to know if Wavetronix would be there for the long haul – to make sure they wouldn’t disappear a few years down the road when they are needed. VINCI specifically asked Wavetronix to commit to ensuring future manufacturing, distribution and development of the HD for at least 20 years.
The recent creation of a Wavetronix office in Southwest France, and the decision to market directly in France, is seen as a sign of Wavetronix’ desire to maintain sustainability.
“The recent investment of Wavetronix in the French market is proof of sustainability over the long term and reinforces our decision to deploy this new radar technology on our network,” Criaud says.
In 2014, VINCI deployed around 30 SmartSensor HD stations on the A11 highway between Chartes and Le Mans and on the A10 highway between Orléans and Tours. An additional 15 HD stations are expected to be installed in 2015.
Balancing on a high wire and balancing the conflicting responsibilities of a transportation department are quite similar. They both require the courage and fortitude to step out into the unknown and they both are significantly easier if a dependable tool is utilized. For a high wire walker, that tool is a perfectly balanced pole; for VINCI Autoroutes’ Cofiroute network, that tool is SmartSensor HD. After having proved the HD’s technology in extensive testing and assured of Wavetronix’ dedication to the French ITS market, VINCI is ready to take the next step in creating intelligent transportation systems and providing superior service to its millions of customers.
