Progressing work zone safety systems

David Crawford investigates progress in a key safety area - work zones

Highway construction zone safety is taken seriously enough in the US to merit a special spring National Work Zone Awareness Week, which in 2010 ran from 19-23 April. Headed by the 324 US Department of Transportation's 831 Federal Highway Administration (FHWA), this aims to reduce an annual toll of work zone deaths - 720 in 2008 (an average of one every 10 hours) with more than 40,000 traffic injuries (an average of one every 13 minutes).

The 2010 focus was on inattentive driving around work zones. Among the most common distracting activities listed by the US 834 National Highway Traffic Safety Administration (NHTSA) are using a mobile phone, or a PDA or navigation system - highlighting the risks counterbalancing the benefits of modern communications technologies being used inside vehicles.

In the long term, the FHWA's emphasis is on the importance of detailed pre-planning for road construction work. Tracy Scriba, who leads on ITS for the FHWA's Work Zone Mobility and Safety Team, stresses the importance of road agencies fully understanding the likely work zone impacts of projects and taking appropriate early actions to manage them.

The key, she says, is using appropriate modelling and simulation tools to carry out effective analysis: "The results from analysing work zone impacts can help an agency improve its decision-making as well as its overall understanding of the mobility, financial, environmental, safety and user cost aspects of its decisions".

The FHWA has now published a series of specially developed guides to help agencies use the tools to develop realistic and achievable Transportation Management Plans (TMPs). Work zone impact analysis, Scriba points out, may involve a high-level, qualitative review for some projects and a detailed, quantitative analysis for others. Key considerations include: mobility and safety impacts at both corridor and the network levels; the combined impacts of concurrent projects in close proximity; and impacts on emergency evacuation routes.

ATSSA's role

A key player alongside the FHWA is the 833 American Traffic Safety Services Association (ATSSA) which, in 2009, issued a new Manual on Uniform Traffic Control Devices (MUTCD). In February 2010, it presented its latest Innovation Awards, for exhibitors at its 40th Annual Convention and Traffic Expo, in San Antonio, Texas, which illustrate some of the new thinking that is currently under way in the highway safety area in North America.

One winner was the Texas, US-based arm of Croatian company 133 Telegra, with its LED Variable Speed Matrix product. This was developed to deliver accurate vehicle speed alerts with a trailer-mounted, fuel cell-powered version for use in work zones. Its optical system allows for options including LEDs flashing in red when a driver motorist exceeds the speed limit by a predetermined parameter, or strobing lights to indicate any over-limit speed.

Another winner was Montreal, Canada-headquartered 538 Versilis. Its SwiftGate remote-controlled, solar-powered series of pivoting gate modules, when activated, creates a continuous obstacle line to act as a deterrent to traffic. The system, which can be controlled by an RF unit, mobile phone or Web-based application, is currently operational on Highway A-13 in Montreal.

Before its installation, highway workers had manually to close a lane four times a day to move a median on the Louis Bisson Bridge, on a curved road section with vehicles passing at 100km/h or more. The company claims that activation can be effected within five minutes.

State programmes

All US states have their own work zone safety programmes. One of the most active in the field of ITS applications is the 1747 Virginia Department of Transportation (VDOT), which maintains the third-largest state roadway system in the US.

It has already created its own version of the MUTCD to include stronger requirements for temporary traffic management: "The use of larger, more visible and closer spaced traffic control devices has played an important role in reducing the number of work zone crashes we experience every year," VDOT's Marshall Barnhill told ITS International.

VDOT's goal is to reduce work zone crashes to below 2,000 a year and deaths to zero per year. Among recent implementations of ITS technology, it has effected one of the earliest US installations of Variable Speed Limits (VSLs) at a work zone in the highly complex, multi-year, 13km Woodrow Wilson Bridge project in the Northern Virginia/ Washington, DC area.

The system constantly assesses traffic conditions through in-road sensors and uses an algorithm to assign optimal speed limits, which change automatically in response to travel flows, for posting on upstream changeable message signs. Initially deployed only when construction required lane closures, the VSL programme was expanded in May 2009 to full-time use.

A recent report from the Virginia Transportation Research Council on the effectiveness of VSL recommends that VDOT continues to pursue the technology, but "carefully to scrutinise" issues of algorithm design and VSL sign placement. Its cost/benefit analysis indicates that the technology may be most appropriate for long-term applications.

European projects

Recognising the value of international experience, the 1841 UK Highways Agency (HA), which manages the 8,000km English motorway and major trunk road network, is about to publish a report on the relevance of good practice in other countries, compiled for it by UK transport consultancy 491 TRL. The Agency's own new Road Worker Safety Strategy, published in November 2009, highlights the importance of removing as many workers as possible from live carriageways, with a 2016 goal of 'Exposure Zero'.

It plans, for example, to make greater use of electronic signage to avoid the need for on-road equipment that has to be physically put in place. Specifically it is exploring, in the light of Scottish and Welsh practice, scope for a wider range of variable message sign legends (to tell motorists when live personnel are working at the site).

It also now has available a rapid-deployment version of UK company 126 Speed Check Services's SPECS average speed camera system (SPECS-RD), which TRL has successfully tested for it on motorways in the English West Midlands. The HA sees its potential as a deterrent at, for example, short-term work zones where installing full-scale speed monitoring would not be economic.

A new TRL decision support tool of interest to the HA is GPS Traffic Viewer (GPS TV), which can use traffic speed and location data to enable assessment of the impact of roadworks by providing user-friendly visualisation. "This can be very useful in locating potential accident sites when flow data isn't available," TRL's Iain Rillie told ITS International.

In Sweden, June 2010 sees the first product release of e-Road Safety (ERS), a roadworks information and warning system based on the identification and location of operating personnel and, eventually, equipment. Swedish ITS company VTS, which owns and will market ERS, has developed it in collaboration with road maintenance provider 837 Svevia and with the support of the Swedish Road Administration.

"We recognise," Svevia's ITS & Traffic Safety R&D Coordinator Urban Ericsson told ITS International, "that the approach for major road construction sites is often to build a physical traffic environment that prevents speeding. Where this is not possible, however, we need a complementary ITS-based product." As typical applications, he points to roundabout construction, bridge repairs or paving train movements.

ERS uses radar units to measure the speed and identify the type of vehicle approaching the work zone, initially from a point between 200 and 300m upstream. If the vehicle is moving too fast, or is an HGV (creating the risk of slipstream close to the work zone boundary), the system alerts construction workers via a vibrating wristband or backstrip (depending on situation and choice) which is designed to overcome the problem of site noise.

At around 50m upstream, a second radar unit rechecks the vehicle. If this is still moving too fast, workers receive a second warning while the system also activates a message sign warning drivers 'DU KÖR FÖR FORT' ('You are driving too fast').

Within the work zone, it then measures the vehicle speed for a third time, on this occasion from the rear, and, if it is still travelling too fast, activates a second warning sign for drivers.

ERS positions construction workers (and plant) using a high-accuracy local system. "We don't use GPS because its accuracy is too low", says Ericsson. "But, as a later step, we will evaluate the EU's new Galileo array to see if it is accurate enough."

In Germany, the government-funded 2008-2012 Safe and Intelligent Mobility Testfield Germany (SIM-TD) project includes development of a roadworks information and navigation system in its wide-ranging car-to-x communications emit. Project leader 2069 Daimler AG highlights the role of modern sensor systems in surveying vehicles' surroundings and giving drivers more useful warnings to avoid collisions.

In the rural roads scenario - one of three based on specific highway types - the focus is on testing systems for obstacle warning and information on construction sites.