What are flexible road safety barriers and how do they work?
Flexible road safety barriers are safety barriers built from steel wire ropes mounted on weak posts. Like all other road safety barriers, their main purpose is to stop vehicles leaving the road and colliding with solid objects such as trees, poles or other vehicles. They are designed to ‘catch’ vehicles before they leave the road; the cables flex, slowing the vehicle and pushing it back into the lane. Depending on the speed and angle of impact, a number of posts may be bent over. This flexibility means that the system absorbs impact energy, reducing the force on the people in the vehicle, which means fewer and less severe injuries. They are designed so no part of them can penetrate the passenger compartment of a vehicle, and the vehicle remains upright. Their design means after impact a vehicle won’t be shunted into an adjacent traffic lane. Flexible road safety barriers are ideal for New Zealand roads as they can be installed without having to significantly widen the road. There’s more information on nzta.govt.nz/wire-rope-safety-barriers (external link)
How effective are these barriers when they are placed on the side of the road?
Flexible road safety barriers on the side of the road reduce the likelihood of death and serious injury from run-off the road crashes by 65 per cent.
Who came up with the idea of barriers?
The use of barriers is based on best practice models overseas that have been adapted to New Zealand conditions.
Are flexible road safety barriers visible at night and when it is rainy and foggy?
Flexible road safety barriers are made from galvanised steel which is silver and is highly reflective, so they can be seen when visibility is low. In addition, there are reflectors on every tenth post which means the barriers can be easily seen when visibility is low.
Are flexible road safety barriers dangerous for motorcyclists?
It’s important we help prevent deaths and serious injuries for all motorists, including motorcyclists. We have solid evidence that indicates flexible road safety barriers do not have a ‘cheese cutter’ effect on motorcyclists.
Research shows installing roadside barriers – particularly flexible road safety barriers –reduces motorcycle casualties between 50-60 per cent. This is because motorcyclists are much more likely to survive an impact with a roadside or flexible road safety barrier than an impact with trees, poles or oncoming vehicles.
We’ve studied motorcycle crash data from January 2001 to July 2013. There were 20 motorcycle fatalities during this period caused by riders hitting a roadside barrier.
- Three involved flexible road safety barriers
- 13 involved traditional steel beam barriers
- Four involved other types of barriers.
The results show flexible road safety barriers have around half the fatality rate of steel beam barriers and that concrete barriers are the most dangerous of all to motorcyclists.
Over the same period there were 97 motorcyclist fatalities from collisions with posts or poles, 70 from hitting traffic signs and 93 from crashing into trees.
I believe several countries banned flexible road safety barriers because of the danger to motorcyclists – is this correct?
Flexible road safety barriers continue to be installed widely around the world. Denmark and Norway discontinued the installation of new barriers a few years ago, but that was for political, not technical reasons.
How are the end of the barriers designed?
Like the barriers themselves, the ends of the barriers are designed to be safely crashed into. They meet our technical specifications.
Will it be safe for cyclists to travel on the road once flexible road safety barriers are installed?
Flexible road safety barriers make the rural roads - especially busy ones - safer for cyclists, as they provide protection from cars that lose control and run off the road. Based on feedback from the cycling community and our project teams experience on the corridor we have widened the sealed shoulder across the entire corridor to ensure that we provide a shoulder with of at least 2 meters between the edge of the live lane and the safety barrier.
Have these barriers been tried before, and do they work, or is this an experiment?
A 3.5km-long flexible road safety median barrier was installed on a treacherous section of SH1 Centennial Highway, just north of Wellington, in 2005. In the four years to 2009, following the installation of the barrier and lowering the speed limit to 80kph, there were no fatal or serious injury crashes on the route and just three minor injuries. Since then, the Centennial Highway barrier has been hit more than 100 times without a single death.
A section of flexible road safety barrier installed on SH1 north of Rangiriri in the Waikato in 2009 has reduced deaths and serious injuries by 65 per cent.
The barrier installed on SH58 near Haywards in Hutt Valley and Coast Road in the West Coast have had similar results. Barriers form part of the design of recent expressways, including the Waikato Expressway and Tauranga Eastern Link.
Why are there solid barriers rather than flexible road safety barriers in some locations?
Flexible road safety barriers can only be used for continuous sections of reasonably straight road with only moderate bends. Solid W-Section steel barriers are used for short sections and on tighter bends.
What compensation will homeowners get if they have a flexible road safety barrier in front of their houses, devaluing their properties?
There are no indications property values are reduced in areas where barriers are installed.
Where will buses stop once barriers are installed?
There will be gaps left in side barriers where buses usually stop. Local hail and ride bus services will also be able to pull over safety at accessways to allow passengers on and off the bus.
Where will vehicles be able to pull over once barriers are installed?
Vehicles will be able to pull over at accessways and layby areas at intersections.
How will people pass wide slow-moving agricultural vehicles when side and barriers are installed?
Vehicles will need to wait to pass these vehicles once they have pulled over at an accessway or clearway at an intersection. Typically, there is an accessway every 400 metres.
Travel times and access
Will we have problems coming out of accesses and merging easily into traffic with barriers blocking the use of the shoulder of the road?
There won’t be any changes to the way traffic merges on the road. We’ll confirm exactly where the barriers will go with landowners before they are installed to ensure sight distances at entrances are maintained.
How do I make a right hand turn into my property?
Nothing will change if you want to turn right into your property. If you need to drive or stop on the grass outside your accessway, talk to our design team so they can ensure the shoulder is wide enough to allow your vehicle to stop safely. These discussions have already taken place with some landowners and the shoulder widths opposite affected entrance ways have been adjusted.
How will emergency services get to people in an accident if barriers are installed?
There will be no changes to emergency procedures when side barriers are installed. If there is an accident blocking a lane, and cars are trapped in the lane between the flexible road safety barriers and the accident, turnbuckles installed every 500 metres on the barrier allow a 60-metre-long separable portion of the barrier to be dropped, creating a bypass. Wide driveway accesses along the route will allow trucks to move further off the lane and will provide extra space for emergency services to pass. Emergency vehicles can also use the opposite side of the carriageway to pass queued vehicles and access the incident.
How close will barriers be installed to my accessway?
Barriers are installed a minimum of 12 metres from either side of an accessway. This allows enough space for vehicles to safety pull in or out of accessways.
Will the barriers make roadside maintenance, such as mowing, much more difficult?
There will be some changes in the way in which activities such as mowing and rubbish collection take place. Lawn mowing, for example, will be done differently on different sections of the road. For some sections, a tractor will drive on the shoulder of the road and use a long arm mower to reach over the barrier. Rubbish collection will be carried out by hand and the contractor will park his/her vehicle in an accessway or layby area. There will be no changes to the way in which drainage maintenance is carried out. Drainage contractors will use existing accesses to get behind barriers.
Who will mow the grass berms when side barriers are installed?
The NZ Transport Agency’s network operations team will continue to maintain the roadside.
How will business be affected by the barriers?
We’re not planning to put any barriers outside retail businesses on this stretch of the highway.
Won’t there be more backlogs on the road with traffic building up behind slow vehicles, due to unconfident drivers not wanting to pass in an enclosed narrow fenced area?
The width of lanes won’t be reduced, and existing passing lanes won’t be removed. We will be widening shoulders which will create more space and make passing easier. It won’t be possible for cars to overtake on sections of the road where there is a barrier, as there won’t be enough space for this to happen.
The fact that passing opportunities will be more regulated reduces a driver’s requirement to make a decision about whether it is safe to overtake. This results in less stress for drivers and results in a safer road.
The route and project
Can you install signs advising people that it’s illegal to pass on the painted strip?
Signs will be installed on the southern section of the road.
What happened to the Ohaupo bypass that was proposed years ago?
An Ohaupo bypass was considered by the Ministry of Works in the late 1970s. However, Transit NZ (and later the NZ Transport Agency) did not take this option any further in the strategic studies which were carried out in 2000.
What is the cost of the project?
The project is estimated to cost $3.8m.
Are there plans to add chips to areas where they have been taken away, especially around the barrier that’s been installed at Jary Road?
Existing road markings were removed by jet washing, and this removed the chips as well. This area of the road will be repaired by the Agency’s maintenance team.
There are various areas on the road where water collects and puddles form, and there is a general lack of camber. Are you aware of these areas? What is the plan to repair these defects?
We will be addressing this in 2018. The issue with the water occurs mainly in the median. Neither the issues with the water and the camber of the road are safety issues. The water does drain away slowly in some areas, but this is in the median and not in the traffic lanes. We can confirm that water ponding is not a safety issue.
Ngaroto Road intersection is not safe. Can a RIAWLS (Rural Intersection Advance Warning Sign) be installed as was done in Christchurch?
Our plan is to make it easier for motorists who are turning from Ngaroto Road onto to SH3 to see traffic travelling south from Te Awamutu. We’re going to do this by removing a garage and cutting back the embankment on the south western corner of the intersection. This will increase sight distance from 150 metres to 230 metres, giving drivers more warning of approaching traffic.
Are rumble strips installed near houses noisy?
Rumble strips shouldn’t cause any noise issues for residents. When rumble strips are positioned correctly on the road, they shouldn’t be driven over frequently enough to cause a nuisance. In some areas we are removing or re-aligning existing rumble strips to minimise potential noise issues.
Why don’t you lower the speed limit instead of installing barriers?
We’ve advised the Transport Agency’s safety team the community would like the speed reduced on this section of SH3. We’ve received draft feedback that indicates if engineering improvements are made to this stretch of the road, then the 100km/h speed limit can remain. However, the speed limit could drop to 80km/h from 180m north of Ngaroto and Te Rahu through to Te Awamutu. This is being looked into as part of the Transport Agency’s speed management programme.
Is it safe to install cat’s eyes and rumble strips on roads cyclists travel on?
Cyclists can safely ride over rumble strips. Cat eyes are spaced approximately 20 metres apart so pose minimal risk to cyclists. Because they alert drivers when they are moving out of their lane, cat’s eyes and rumble strips actually increase safety for cyclists by reducing the risk of vehicles hitting them.
Some people who were on your mailing list have been taken off – why is this?
We’re not aware that anyone has been removed from our mailing list. If anyone needs to be added onto our mailing lists, please let us know.
What is the consultation process? When do submissions close?
SH3 is designated in Waipa District Council’s District Plan as a State Highway. The responsibility for the designation – which is defined as the maintenance and improvement of existing highways – is our responsibility. Other provisions of the District Plan don’t apply, and this means there is no formal submission process.
Why were the original four lanes amended to be 2+1 arrangement?
The original lane configuration was amended primarily to improve the resilience and safety along the corridor in particular to make getting into and out of properties and businesses safer. Issues around maintenance along the corridor, and travel time were not significant contributory factors to this decision.
How do turn around facilities work?
On this stretch of the highway, turnaround facilities will allow motorists to turn around safely, rather than having to wait and cross oncoming traffic.
Drivers proceed to the closest intersection or turnaround area where they can turnaround and proceed in their desired direction of travel.
If we spent money on education, crashes wouldn’t happen?
One of the key principles of the Safe Systems approach is around providing a comprehensive systematic approach to road safety this include:
- Safer roads and roadsides
- Safer vehicles
- Safer speeds
- Driver behaviour, enforcement and education
Will changes be made to the access and parking at the cemetery as part of this project?
We have been liaising directly with the Catholic Diocese of Hamilton regarding some proposed improvements to the access and off-road parking at the cemetery. At this stage, they have agreed to allow us to improve both the entrance to the cemetery and the entrance surfacing.
