Vehicle safety aids: At close quarters

From radar-based proximity alarms to auto disablers, we review the range of electronic aids to keep pedestrians and vehicles out of striking distance.


Words: Tina Weadick

Leaving the cinema after watching Star Wars: The Force Awakens, my partner and I were excitedly discussing one particular piece of on-screen tech that had grabbed our attention. Rolling droids, I hear you say? TIE fighters, perhaps? Light sabres, surely? None of the above; the standout piece of kit for us was the latest family car from a well-known German manufacturer advertised before the film started.

Usually, I pay scant attention to ads but as someone who failed her first driving test because of an inability to parallel park, I was intrigued. This car literally parks itself – not just beeping to let the driver know they’re getting too close to a solid object but actually carrying out the manoeuvre and manipulating the steering wheel. Of course, park-assist technology is not new but technology that helps protect real drivers, pedestrians and, in particular, employees is always worth noting.

Today, the biggest strides in proximity-warning and collision-avoidance systems are being made in the mass consumer market, by car manufacturers, but that is partly because reversing alarms, blind-spot monitoring and collision avoidance have been fitted to workplace vehicles for some time now. Despite the availability of such helpful kit, however, the number of incidents involving workplace transport is still worryingly high. Being hit by a moving vehicle is second only to falls from height as the biggest cause of work-related deaths in the UK; these “struck-bys” account for 1,500 serious injuries every year.

No compulsion

There is no legal obligation on employers to equip their workplace vehicles with safety devices above and beyond the standard requirements, such as mirrors and horns. As long as “non-road mobile work equipment” meets the requirements of the Machinery Directive for design and construction, it is compliant. Vehicle manufacturers, for their part, are not obliged to build in advanced safety technology.

In the hierarchy of protection, add-on safety devices are the last line of defence. The Health and Safety Executive (HSE), in its advice to employers on how to minimise workplace transport incidents, advocates creating a safe site – segregating vehicles and pedestrians, avoiding reversing, ensuring good lighting and signage – then a safe vehicle – ensuring it is fit for purpose and well maintained – and finally a safe driver – trained and supervised.

Industry bodies do not press for them either. The Forklift Truck Association, for example, makes only passing reference to safety devices and technology on its website, and its comprehensive range of factsheets does not include one on safety technology.

Though the regulator may not highlight technological aids it does encourage employers wishing to improve workplace transport safety to consider the warning systems fitted to their vehicles, the degree of all-round visibility available to the drivers, and ways to immobilise vehicles. To those ends, its published guidance on the subject acknowledges the assistance provided by the likes of visibility aids and reversing sensors and alarms (http://www.hse.gov.uk/pubns/priced/hsg136.pdf).

Site specifics

So how do you decide which devices will work best on your site and your vehicles? Your first consideration must be the work environment. Is it an open or enclosed, public or private site? How many vehicles are using the site and what are the different types? How does the location and layout of the site affect vehicle movements? How many people are moving around the site and where are the main areas in which they are likely to encounter vehicles?

The next step is to determine the type of system best suited to your activities, bearing in mind that you may require a combination of devices and, if there is more than one operator or contractor on the site, that all systems will need to be compatible and not cancel each other out (or create a cacophony). Proximity-warning and collision-avoidance technology can be broadly categorised as:

  • systems that warn the driver: proximity alarms that sound in the cab, closed-circuit TV systems with an in-cab monitor to give the driver a 360-degree view around the vehicle
  • systems that warn the pedestrian: audible reversing and turning alarms and visible beacons, wearable tags linked to transmitters on the vehicle that alert the wearer when they are in hazardous proximity
  • combined driver/pedestrian warning systems: transponder or tag-based proximity-warning and alert systems that detect personnel around vehicles and alert them and the driver
  • automated systems: these activate when detecting an obstruction, usually stopping the vehicle.

Sensor place

Proximity sensors are, perhaps, the least complex of technological safety aids. They work by alerting the driver to the fact that their vehicle is coming potentially dangerously close to someone – or something. They are generally cheap and easy to fit and, as a result, are common in workplace and commercial vehicles. Their inherent problem is that, certainly early on, they were designed to aid parking, not to alert drivers to pedestrians. They will “beep, beep, beep” at almost anything: the roadside kerb, railings, even heavy rain. In fact, they are often only fitted to the left side of vehicles because putting them on the front and right side can increase driver irritation and lead them to disable the sensors.

The technology has moved on to incorporate cameras and closed-circuit TV systems with sensory detectors that can distinguish human beings from other objects, and provide drivers with a bird’s-eye view of what is going on around their vehicles. The sensors use laser beams, ultrasonic waves, or radar signals. For heavier-duty applications radar is a good choice, because it is less affected by weather and tough working environments.

The most sophisticated systems involve three or four cameras mounted around the vehicle, with the images fed back to a monitor in the driver’s cab. Software analyses the images and lets the driver know, via an alarm or flashing light, if someone is too close. The main advantage of such systems is that the driver has only to focus on one monitor rather than flick between several mirrors and cameras. Some systems are even night vision enabled, or resistant to sun glare. None of this comes cheap and that is its major drawback. It will also be unsuitable for vehicles without an enclosed cab or dump trucks and smaller plant.

Feet first

Reversing and turning alarms and beacons let anyone in the vicinity of a vehicle know that it is about to reverse or make a turn – manoeuvres in which the driver’s view typically is restricted. Though such alarms don’t improve the view for the driver, they do give vulnerable pedestrians notice of the vehicle’s intention and time to take evasive action. They are relatively cheap and easy to retrofit and very straightforward to use. However, they do rely on attention and action by those on foot.

On a busy site with lots of competing noise or flashing lights, an alarm or beacon may not be noticed, or the pedestrian may not be able to work out where the sound is coming from. The shrill and piercing quality of reversing alarms can also be an issue in work environments that are in or close to public areas, especially residential ones. Latest innovations to address these problems include “broadband sound” alarms. Broadband sound comprises a much wider range of frequencies than tonal sound, making it easier to hear – even for those wearing hearing protection – and easier to locate its source. Broadband sound is also directional, meaning it’s heard only in the danger zone, so there is less noise nuisance. Other smart reversing-alarm functionality includes self-adjustment, where the alarm continually adjusts to the ambient noise level, which can fluctuate considerably in a busy work environment. (For more detail on active safety systems in vehicles, bit.ly/1mqdqEh).

Tag team

Though most tag-based proximity systems warn vehicle drivers, some are designed primarily to alert workers nearby. These systems involve installing a generator on the vehicle that creates an electromagnetic field around it to mark hazardous areas. Workers on foot are then fitted with personal alarms that detect the magnetic field and alert them to the hazard.

The vehicle generator is easy to retrofit to any type of machine and pedestrians’ movements into and out of danger zones can be recorded and analysed – to inform future vehicle movement planning, for example. Multiple machines and any number of pedestrians can operate in harmony.

The fact that the alert doesn’t depend on sound makes these systems particularly suitable for sites where the ambient noise is loud. But they can be expensive, especially if large numbers of vehicles and workers have to be fitted with generators and personal devices. Depending on how the warning is delivered – usually in the form of a vibrating signal – repeated alerts may become irritating, or even distracting to the device wearer, who may feel that the device is like the boy who cried wolf, leading them to disable or remove it.

Both sides

In combined systems, all vehicles are fitted with an active reader that has an adjustable range, and all personnel wear tags that communicate with the reader. When a person enters the reader range, an alarm in the vehicle will warn the driver and the transponder being worn by the pedestrian will alert them.

The transponders can work with all sender units, so they will communicate with any number of vehicles fitted with them. Drivers, too, can be issued with transponders, so vehicles can communicate with each other and avoid collisions.

The success of the system relies on the transponder being worn by the workers, because vehicle operators will assume this to be the case. Thus, perhaps, drivers may rely on the system rather than their own vigilance to warn of any hazard.

Cost is also a factor: fitting large machines, such as excavators, with sender units and antennae costs thousands of pounds – without factoring in the transponders for the workers. In addition, this kind of system may not be suitable for smaller, enclosed sites or narrow or linear work areas, as alarms would be going off constantly, causing disruption and irritation among workers.

Emergency stop

All the systems described so far rely on pedestrian workers or vehicle drivers acknowledging and acting on a warning they have received about a hazard. If that doesn’t seem a reliable option, an automated system may be preferable: one that stops or shuts down a vehicle automatically when it approaches a fixed hazard such as overhead power lines, or whenever anyone enters the safety zone.

Generally, such collision-avoidance (as opposed to warning/alert) systems are linked to the brakes or isolation system of the vehicle, so they cut out immediately on detecting a hazard, obviating the need for human intervention. Some can be set at different sensitivities, to kick in at specific distances from an obstruction, taking into account the speed
of the vehicle and stopping times. Some can also be set to deactivate if they sense the driver taking avoidance action.

A major disadvantage of such systems is potential injury to the driver caused by the vehicle suddenly stopping. For this reason, a suitable form of restraint, such as seatbelts, will have to be provided and the risk of whiplash assessed. Retrofitting is generally not an option, particularly for more sophisticated systems.

Automatic speed-reduction systems work particularly well for indoor vehicles. Forklifts, order pickers and reach trucks can be fitted with sensors that automatically reduce travelling speed in high-risk areas and situations. In the case of trucks that shuttle between outdoor and indoor work areas, there are even systems that can differentiate between the two environments and adjust maximum travelling speed accordingly.

Behavioural observation

There is no doubt that we are living in times that are increasingly technology enabled – some would say technology controlled, and that the systems and devices outlined above will only grow in number and degree of sophistication. Nevertheless, it remains the case that all of these systems, even the automated ones, have a human at their heart. Though the biggest pro for each of them is the reliability of the technology – though they still depend on humans for testing and maintenance – the biggest con is undoubtedly human error, or inattention, or plain disregard.

The bottom line is that vehicle safety systems, in particular active ones, allow drivers to pay less attention to the road, or environment. As far back as 1908, psychologists Robert Yerkes and John Dodson described the relationship between arousal and performance thus: give people too little to pay attention to and they will become complacent. If people rely on the technology too much to keep them out of trouble, or perhaps are unsure about what exactly it can and cannot do, the technology may end up exacerbating the problems it was designed to address – or even create new ones.

The HSE has flagged up this reliance on the technology over drivers’ and pedestrians’ own hazard perception as a potential drawback of proximity warning systems.

And then there’s the multitasking issue. According to a research review by the Transport Research Laboratory, humans cannot do two things well at the same time (bit.ly/20wSDhV). Driving is a complex skill and requires various cognitive processes. Taking on another task, such as checking cameras and monitors, can inhibit the driver from paying enough attention to all the activities required for safe driving and thus fail to process all the information they receive. This is the same argument that applies to using hands-free mobile phones on the road.

As with most safety issues, training and communication are key – particularly for pedestrians who, because they are in charge of themselves only rather than a multi-tonne piece of dangerous machinery, are likely to be more complacent than vehicle operators. Any system or device used, its operation, components and effects – particularly if not used properly, or at all – must be thoroughly explained to all personnel, as must the danger of relying on such systems in isolation. It’s also good practice to make someone responsible for ensuring devices are worn and the system is being used properly and heeded.

As mentioned, some systems allow data – such as system breaches – to be logged and analysed. The lessons learned should be shared with workers and used to update workplace transport risk assessments.

*Thanks to Brigade Electronics for its help with this article. 


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  • I wonder if as mass market

    Permalink Submitted by Duncan Brown on 18 March 2016 - 03:40 pm

    I wonder if as mass market consumer tech in this area becomes more common whether these systems will become cheaper too?


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