Application: Wireless traffic monitors

With 850 km of turnpike to manage and 188 million vehicles a year to safely guide through, the Pennsylvania Turnpike in the US is not only historic — it was the first turnpike in the nation when commissioned in 1940 — but an essential east-west artery for commuters, tourists and freight travelling through the Keystone State.

Now in its sixth decade of operation, the road has been upgraded, widened and lengthened many times in the years since it inception.

The Pennsylvania Turnpike Commission has worked continuously to make travel faster and safer.

A pilot program deployed in June 2008 is one element of a larger plan to improve safety, reduce response time for first responders and alert motorists more quickly to accidents and weather-related incidents.

Allen Baldwin, director of operations and incident management with the commission, describes how it is extending the implementation of Intelligent Transportation Systems (ITS).

“We maintain a traffic operations centre in Harrisburg that continuously monitors Turnpike activities via an extensive radio system.

“Road conditions, construction status and weather conditions are all monitored at the centre, which also serves as the focal point for all turnpike incident management,” Baldwin says.

For traveller alerts, the centre relies on a variety of incident management tools such as fixed and transportable variable message signs and AM radio broadcasts about weather and other emergency situations that might affect safety and speed. This information is also available via touch-tone telephone, mobile phone or the internet.

The ultimate solution is to automate the real-time visual monitoring of 850 km of road, much of it rural, for 24 hours a day, seven days a week.

Remote, weather-resistant video cameras and related sensing devices can be connected to the existing LAN/WAN network to supply a continuous feed to the operation centre, which in turn can be monitored by staff.

Many necessary camera locations are far from accessible power lines and LAN/WAN connectivity via land lines, either T1 or fibre optic, are either nonexistent or too expensive to contemplate.

A reliable, self-powered wireless package capable of delivering real-time images and data to accessible LAN/WAN nodes would be ideal.

But finding such a ready-made package was another matter. “We looked for off-the-shelf solutions, but weren’t satisfied with what was available,” says Dan Dunchock, manager, communications systems for the Turnpike.

“So we spent about two years in developing our own solution.”

That required a mix of technologies and the willingness of several vendors to help the commission solve the various problems that invariably surface in such a project.

Barriers, for example, would suffice for operating the cameras and wireless components, but keeping them charged was a problem.

“Solar panels alone aren’t sufficient for reliable power in our climate,” says Dunchock.

“So we worked with IdaTech, an Oregon-based manufacturer of backup fuel cell systems, to develop a hybrid solar/fuel-cell solution that provides reliable remote power to charge the batteries in any weather.

“Now we have a reliable source of power that can run for about two or three months, depending on cloud cover and the need to augment the solar panels, on a single tank of fuel.”

The fuel, a mixture of water and methane, produces hydrogen to run the fuel cell. “The residue is water,” says Dunchock, and the fuel cell itself is very compact.

The next step was to add a wireless transmission system to the CCTV camera and power supply. “We tested several wireless broadband products but the only one that worked to our satisfaction was Tyco Electronics’ VIDA Broadband system.

This uses the WiMAX protocol over the 4.9 GHz band licensed for public safety use, which greatly reduces the problems of interference.

The other systems relied on Wi-Fi or proprietary protocols, most of which use unlicensed frequencies that are far too susceptible to interference.

When assembled as a unit, the standalone remote wireless video system, which the turnpike calls a POP (point of placement) stand, is compact and easily deployed.

In June, 2008, a test unit was ready for installation.

The system has been feeding images received in the centre since late June, and all signs point to being able to expand the pilot program.

In practice, the POP stand automatically alerts those in the centre when traffic slows to about 30 km an hour.

The real-time images allow operators to see what the problem is and ultimately will help the centre in assessing the kind of response that may be needed.

If there is an accident involving a hazardous materials spill, for example, seeing a hazmat sign on a truck lets the centre know there is a potentially serious problem.

In addition to providing real-time images, a short fibre-optic cable monitors an adjacent traffic alert sign that notifies travellers to tune in to the 1640 AM band on their radio for information.

In the past, they would send a DTMF signal over the radio system to turn on flashing lights to let drivers know there was an emergency message being broadcast.

But there was no way to monitor the signage and confirm that the lights were on.

With the POP stand, a blinking light in one corner of the video images received in the centre lets it know whether it’s on or off.

With the successful deployment of the first POP stand, the commission will continue to test and evaluate the unit and expand deployment in critical areas as time and budget allow.

Roger Kohr, Tyco Electronics sales representative, notes that the capabilities of information sharing between an expanded ITS 4.9 GHz network and future public safety 4.9 GHz networks across municipalities, states and even regions is an intriguing possibility.