Road Construction sites are dangerous for both construction workers and motorists. Changed traffic conditions, a multitude of warning signs, narrower lanes and varied speed zones increase the chance of driver error. The increased chance of driver error means that the work zone is a dangerous place for road workers and motorists, requiring a layer of positive protection against driver error.
Bollards, cones, and barrels offer no protection to the workers or motorists, and do little other than provide delineation. They do not prevent vehicles from entering a work site and do not stop a distracted worker or piece of construction equipment entering live traffic.
There is a higher risk of injury or death of a worker at poorly protected sites, and every injury or death comes at a severe cost to the contractor, the worker, the driver and the community in general.
Tested temporary barriers provide positive protection and mitigate the risk of driver intrusion into the work zone and the resultant serious injury or death. Barriers in a work site help cause ‘side friction’ to induce slower driving and provide positive protection for the worker and the motorist.
Contractors who deploy temporary barriers recognize the value of the safety to the workers and understand the true cost of failing to properly protect workers. Temporary barriers are often used because they are mandatory in a contract. However, even when not mandated contractors know that temporary barriers are an effective Risk Management tool ensuring best practices are used to protect their work force.
At the basic level, all temporary barriers are tested to international standards MASH16 (AS/NZS 3845:2015) (replacing NCHRP350 & AS/NZS 3845:1999) or EN1317-2. All temporary barriers are evaluated by local road authorities who publish the test data, including deflection, working widths, and minimum lengths of installation based on the laboratory testing submitted for evaluation.
The issue with the published data is that it is the result of laboratory tests. You can look at the crash tests of most of your temporary barrier options on YouTube and you will see that they are all done with the same size of vehicles on straight line installations with impact angles at 25 degrees.
As a traffic planner or site safety manager, you have to make decisions about which temporary barrier to select and how it will be deployed based on this limited information.
Unless you are working on a freeway, motorway or large urban road, the chances are your installation will not be a long straight line, will not be capable of receiving an impact at 25 degrees and vehicles may not be traveling at exactly 70kph (45 mph) or 100 kph (62 mph), as in the laboratory tests.
The information in the approval documents offers limited help in determining deflections or general temporary barrier performance to suit your work site when your work site doesn’t match the laboratory test track.
Work sites usually require a site-specific risk analysis, and to make this analysis you need more information about barrier systems than provided by road authority acceptance documents.
Traffic management plans and site-specific risk analysis must answer many questions to ensure the safest possible work site, some of the information (but not all) required:
- How many lanes of traffic can impact the barrier?
- What is the nominated speed of the work site?
- Is there a different, higher, speed of the work site in non-working hours?
- How much room is there to allow for barrier movement if it is hit?
- I need to redirect pedestrians around a job site onto the carriageway, how much room should I allow for barrier movement?
- How does the crash cushion at the end of the system affect the layout of the barriers and where I can work?
- My work site is on a curve, will that affect performance?
- The barrier cannot be installed exactly as approved, what do I do?
All of these questions, and others, will affect the expected performance of the selected temporary barrier at your site
What can the contractor or traffic planner do?
- Complete a site-specific risk assessment with support from the temporary barrier manufacturer. The manufacturer is your best source of knowledge when it comes to expected performance in non-standard situations.
All temporary barrier manufacturers are interested in their barriers being used properly to provide the protection that is expected on your site.
- Complete a site-specific risk assessment with support from an expert with years of practical experience in the use, and limitations of different temporary barrier types and how they can be expected to perform on your site.
Practical knowledge, built up over decades, injected in to your site-specific risk analysis or traffic plan will help you determine the best possible scenario for your site.