Having recently been involved in an advisory capacity for a client in the application of safety systems in the construction environment I thought it worthy of considering the implications of safety and machine control.

The Statistics
Regardless of what industry you are involved in, safety in the workplace is the number one priority. Safety can be achieved through the application of legislative requirements, education, correct working practices, personal responsibility, personal awareness, and any associated and subsequent  use of safety related product and tools. However, even after applying such criteria, there are still too many accidents occurring when working with or near mobile machinery in the workplace. For example each year in the UK there about 8000 lift truck accidents resulting in injury and on average 10 of them are fatal. Over all industries, vehicles account for 25% of fatal accidents in the workplace, this figure rises to 60% of fatal accidents in the quarrying industry. These figures rise significantly for the USA with 20,000 fork lift truck related injuries and nearly 100 fatalities occurring every year ! The USA mining industry has similar tales of woe with powered haulage accounting for the majority of fatalities with 53 caused by crushing by mobile equipment between the years 1995 and 1998.

With respect to the UK construction industry the UK Health and Safety Executive issue the following general statistics :
* Construction has the largest number of fatal injuries of the main industry groups. In 2008/09 there were 53 fatal injuries giving at rate of 2.5 per 100 000 workers. This is the third highest rate of fatal injuries, behind agriculture and extractive industries.
* The rate of fatal injuries in construction over the past decade has shown a general downward trend, the rate for 2008/09 being less than half the rate in 2000/01 (2.5 compared to 5.9 per 100,000). The rate has decreased by 34% in the past 3 years.
* Since 1999/2000 the rate of reported major injuries to employees in construction has fallen steadily. Despite this falling trend, the rate of major injury in construction is the highest of any main industry group (254.1 per 100 000 employees in 2008/09).
* Relative to other industries, a higher proportion of reported injuries were caused by falls from height, falling objects, contact with moving machinery, collapses/overturns and electricity.
* However, the rate of self-reported work-related ill health in 2008/09 was of a similar order to that for all industries, based on results from the Labour Force Survey (LFS).
* In 2008/09, the LFS showed that 3 million working days (full-day equivalent) were lost in this industry due to workplace injury and work-related ill health.
Clearly the trend for reported injuries has fallen, but the numbers are still very high.

With regards to specific construction activities the US Department of Occupational Safety and Health Administration says :
* Approximately 75 percent of the fatalities due to being struck by a machine involve heavy construction equipment such as trucks, cranes, graders, or scrapers. Many of the fatalities caused by being struck by material involve poor rigging of loads being moved or poor storage of materials.

* Seventy-nine percent of trenching fatalities occur in trenches less than 15 feet deep. Thirty-eight percent of the fatalities occur in trenches less than 10 feet deep.

There is an awful lot of statistical data out there, I am not going to regurgitate it all and have only chosen sample facts to indicate the scale of the problem.

Legislation
There is a variety of legislation and guidance available in reducing risks from operating vehicles with duties on manufacturers, suppliers users and pedestrians. In addition to general legislation there is industry sector specific legislation.
The following lists good practice in terms of reducing transport risks and ensuring a safe system of work :
The workplace should:

• Remove the need for reversing where possible.
• Separate pedestrians from operation of fork-lifts and other vehicles.
• Exclude people from areas in which vehicles are permitted to reverse.
• Have clearly defined traffic areas and minimise the distance vehicles have to reverse.
• Have speed restrictions and signs inside and outside the workplace (implementing lower speed limits for congested areas).
• Use mirrors and visual aids at corners and obscured hazards.
• Have adequate lighting.
• Use traffic signs/traffic control where appropriate.
• Have loading areas isolated from high traffic areas.
• Ensure give way rules are enforced where applicable.
• Employ flexible or transparent doors where practicable.
• Implement vehicle maintenance and reporting procedures.
• Ensure parking areas are restricted to authorised people.
• Make sure all staff are adequately trained.
• Use a permit to work scheme with restrictions on vehicle key access.
• Use a properly trained guide and decide how the driver is to maintain contact.
• Ensure all visiting drivers are adequately briefed of hazards.
• Ensure all vehicle manoeuvres are properly supervised.
• Increase the area the driver can see by vehicle choice or load modification.
• Where load obscures forward vision, drive in reverse (except up ramps).
• Fit reversing alarms and other safety devices.
• Switch on warning lights when a vehicle is in use.
• Identify doorways, passages or pathways where pedestrians or vehicles may suddenly appear.
• Sound warning devices when going through doorways, around blind corners or when starting to reverse.

So where does machine control fit into all of this ??

The above good practice list may just seem like common sense, but  how does machine control fit into all of this ? Machine control may not offer a complete solution for site safety related issues, but it can certainly go a long way in complementing good practice and other safety monitoring systems.

The whole purpose of machine control is to improve efficiency and productivity and it achieves this by working quicker, right the first time, and by needing less people on the work site.

Reducing the number of people on site
Let’s look at the OHSA statement :

* Seventy-nine percent of trenching fatalities occur in trenches less than 15 feet deep. Thirty-eight percent of the fatalities occur in trenches less than 10 feet deep.

Clearly people are being killed by being in the trench. The statement does not include the activity or operation in the trench, but it can be assumed that being in the trench when directing large construction machinery in an excavation task is hazardous. What is one of the major selling points we use when explaining the benefits of Machine Control ?  “Machine control removes the need for the man in the trench”.

Remember, machine control not only reduces the risk in the dig, but also removes the need for additional support personnel on site whether they are fixing batter rails and benchmarks, checking accuracy or guiding machinery, the technology helps by removing these people from the site and therefore being potential targets for any number of large haulage vehicles on site. Any number of legislative requirements and guidelines will never be as effective as not having the personnel on the site in the first place.
So, assuming we have reduced the number of people on site what next?

Vehicle Collisions
Vehicle collisions occur on site for any number of reasons even with a range of safety accessories installed on the vehicle – mirrors, cameras, radar etc. A collision will still come down to an operator not being aware of a potential target or being aware and taking a risk. The latter we can’t do anything about with technology – that is the domain of education and site management and policing, but the former we can.

A vehicle can collide with :
* Static object
* Another vehicle(s)
* Personnel

Static Object Collisions
Static object collisions are a prime example of what machine control is capable of helping in averting. A full 3D machine control solution can have the objects or avoidance zones pre-programmed into the design model. As the system knows where the machine is in relation to the object then the system can alert the operator when he nears the object in question giving him plenty of time to react. This can be as simple an object as a gas well on a landfill site. This clearly requires the use of precision GPS and most importantly relies on the GPS not failing at a critical moment. This may not be too important for some static objects which whilst expensive damage may be caused there will not be a fatality from the collision. However if there is the potential for a fatality then GPS alone is not good enough – more on that later.

During dredging operations damaging a barge with an excavator because the operator cannot see the bucket in relation to the pontoon occurs more often than you might think. Applying machine control can assist by warning the operator if the bucket nears the barge.
Machine control can also be applied to surround the machine with a virtual protection cage. If any of the machine equipment enters the virtual cage limits then appropriate warning are activated. This is of particular use for machines with large swinging grabs, extending cabs or multiple articulations.

Vehicle – Vehicle Collisions
Similarly, if all vehicles on site are equipped with GPS then it is possible for them to know where they are in relation to each other. This requires not only the machine control systems to have GPS, but all other vehicles on the busy work site. This also requires a step up in the software and additional high speed communications for the data to be relayed between vehicles.  As vehicles approach each other the system software can warn the driver / operator giving them plenty of time to take evasive action if necessary. Ideally all data will be passed to a site office base computer for monitoring and recording of the data.

As well as use on busy construction sites this can also be applied to sites such as aggregate depots or mines. However the same fatality rule should occur here as well – if a fatality is possible then GPS alone is not good enough.

Whilst GPS is a reliable tool it can suffer from problems that can cause it to give incorrect data –satellite availability, precision, multipath errors, loss of signal due to the environment (surrounding buildings, other vehicles, gantries, foliage etc), loss of base correction signals and data etc. Because of this possibility of a fault occurring then a secondary system is recommended giving system redundancy in the event of GPS failure.  GPS is good for monitoring and positioning but is not reliable enough to be used as a single preventative measure against possible fatalities and like all safety tools should be used as guidance alongside the implementation of good working practices .

For information : the quantity of redundant systems can be increased dependant upon the nature of the application – the Airbus A340 has 5 flight computers any of which can fly the aircraft on its own with a reduction in operational features as the number of computer failures increase.

So what additional measures can be used to complement machine control and safety :

1    Good working practices – see the list at the beginning of this article
2    Additional aids / tools, fitted as standard to machines – mirrors, reversing cameras, reversing / forward looking radar
3    Personnel / pedestrian detection

Items 1 and 2 are applied as standard, however visual aids are passive devices and require a predetermined action to use them effectively – actions such as looking in a mirror can be forgotten or neglected and are not as good as additional automatic detection (active system) which brings us on to  item 3.....

Avoiding personnel / pedestrian collisions
From the point of view of the pedestrian the obvious thing to say is be seen – wear high viz and all recommended PPE (personal protective equipment, so even if a collision occurs with a moving vehicle, damage potential can be reduced). Follow site rules and keep to pathways etc.  However there are always circumstances which require being in hazardous areas. GPS is not at the stage where it can be applied to individuals in an ergonomic and economic manner so we need another way of detecting personnel and warning machine operators and drivers.

This is where RF proximity detection systems are very effective.  By installing an active system such as this (vehicle sensor units and RF tags on personnel) then an effective warning system can be created giving indication that person(s) are within a predefined warning zone. This does not give precise location of the personnel, but can warn the machine driver both audibly and visually of their presence, and in some cases can be wired into the machine to cease motion or similar action. This is more effective than reliance on passive systems as the warning occurs without the need for any positive action from the machine operator / driver.

RF systems can also be applied such that machine to machine detection is possible  (hence it can assist in avoiding vehicle to vehicle collisions)and most of these systems come with incident data logging etc. Integrating this type of system with machine control and GPS means that the location of any incidents can be recorded as well.

I seem to have strayed off the beaten track with regards to machine control safety, safety is a huge subject area and I have barely scratched the surface, but I think it is important to be aware of the limitations of what can be achieved by the machine control system alone and that site safety is improved by the implementation of a range of measures and technologies. To quote a line from a long running US TV series .... “Let’s be careful out  there...”

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