Crash test standards: for people outside cars

car crashes with pedestriansThe safest way to protect people from cars is to give people segregated space; separate paths to walk, cycle and ride motorbikes. Cars and people don't mix: we need to democratise design so the needs of people are prioritised. However, car manufacturers have a social corporate responsibility to design their vehicles in ways that mitigate levels of injuries to people on foot, bicycles, other non-motorised transport, and motorbikes in collisions with those people.

Collectively, people outside a vehicle and using a road are described by road safety professionals as vulnerable road users (VRUs). For ease of understanding and speed of reading, we use this term in this fact page, even though it's jargon and dehumanising. 

Due to size, weight and rigidity, a collision between a vehicle and a human body can have catastrophic consequences at any speed. Statistics show VRUs are disproportionately casualties in road crashes compared with people inside vehicles.

For example, just over half the deaths on roads in Britain are VRUs. It's the same in Chile. In other countries it's even higher; in South Korea, about two thirds of deaths on roads are VRUs.[1] 

The risk of using roads as a VRU is higher than as a vehicle occupant. Britain's Department for Transport calculates that, per billion miles travelled across the British road network, for every car occupant who dies, more than 21 cyclists die and more than 24 motorcyclists die [2]. 

What happens when a car collides with a person? 

Studies have found many injuries incurred by pedestrians in collisions with cars are to their lower limbs [3]. Less than one in seven pedestrian injuries occur from contact with the windscreen (usually the head hitting the windscreen) [4] [5]. However, studies have also found that most (eight out of ten) deaths and serious injuries of pedestrians are caused by head injuries, and most of these (eight out of ten) are in collisions with the windscreen [6] [7].

In a collision between the front of a normal saloon-style car and a pedestrian, the car can hit the pedestrian’s leg, causing the pedestrian’s body to rotate towards the car at the ‘bonnet leading edge’ (the angle between the vertical bumper and the horizontal bonnet top, known as the BLE), slide up the bonnet and hit their head and upper body on either the bonnet, the windscreen or an A pillar (the solid frame of the car at either side of the windscreen).

Increasingly, modern saloon-style cars have longer, angled windscreens and shorter bonnets than in the past, increasing likelihood of head impact with either the windscreen or the A pillar. However, not all cars are this shape. Notably there has been a significant divergence in the height of BLEs among different car models. Large cars designed for off-road purposes, known as SUVs, have typically much higher BLEs. SUVs in Europe have increased from less than one in 10 cars ten years ago to around one in five today [8].

It is not known how diversity in shape of cars or any other aspect of their design and road use (for example speed) has specifically affected real world injuries of VRUs, due to lack of close investigation and collation of large data sets regarding what happens in crashes and what measures are saving lives, or not. For example, it is only hypothesised that, in collisions with children and small adults, a high BLE may hit these people's heads and upper bodies and not result in them rotating and sliding up onto the bonnet.

In a "real world" collision, a VRU who is hit by one vehicle may consequently be flung into the path of another vehicle or object.

What are car manufacturers doing? 

Car manufacturers can fit bonnets and bumpers that can be described as "energy absorbing", meaning the car's outer shell deforms inwards as the person's body hits it. The BLE can also be designed to be more energy absorbing. 

Manufacturers can also address the central windscreen area’s “stiffness” upon impact with a head. They can change the windscreen angle, shape, thickness and the glue bonding the windscreen to the car and distance to dashboard. The dashboard itself can also be be made more forgiving. [9] Bonnets can also be designed to lift up on impact, to try to prevent a head hitting a windscreen. 

To overcome the problem of hard A pillars, some manufacturers have started to fit external air bags, for example Volvo. External air bags could also be fitted to a BLE. 

What are governments doing? 

The European Union is an example of one region of the world that is doing something about VRU safety. It requires car manufacturers to fit cars with bonnets and bumpers that can be described as energy absorbing, and pass mandatory impact (crash) tests to the front of the car in laboratory conditions, colliding the car and an ‘impactor’. The impactor is a dummy body part. The test results must meet ‘injury-based performance limits’ to pass (in other words, when the impactor and the vehicle collide, the damage incurred to the impactor mustn’t be over a given threshold). 

The mandatory crash tests are currently:
a. a lower leg form hitting a bumper;
b. an adult’s head form hitting the bonnet in the “adult zone” (place it is likely to hit);
c. a child’s head form hitting the bonnet in the “child zone”.

For the head form impact tests, two impactors are used at 35kph. The child and adult head forms have a mass of 3.5kg and 4.5kg respectively to represent a child’s head (or small adult’s head) and adult head. The different head forms are used to impact in different “zones” (places on the bonnet where the heads are thought more likely to land.) The adult head form test is not carried out on short bonnet tops (where the measurement from the ground at the front of the vehicle to the windscreen edge is 1.7metres or less) because it is estimated the adult head form would, on these cars, hit the windscreen not the bonnet.

These tests have been written into a UN regulation, number 127, on pedestrian safety. 

What more needs to be done? 

Lots needs to be done. As a bare minimum, all countries need to adopt UN Regulation 127 or equivalent and its requirement for new models sold to be crash tested to the standards in this regulation.

The tests required under UN Regulation 127 are thought not to be fully representative of what happens in "real world" crashes. Heads hit windscreens or A pillars. Bodies pivot around bonnet leading edges (BLE). Crash testing of head and body part impactors against windscreens, A pillars and the BLE needs to be legislated. In the European Union, some of this testing is carried out for "monitoring" purposes only; in essence, to see if manufacturers' new models can pass these tests, rather than to stop these models hitting European streets. These "monitoring" tests are: an adult's head form against a windscreen, and an adult's upper leg form against the BLE.

Cars have performed badly in these European tests. Out of 323 vehicles subjected to the monitoring-only tests for a head form hitting a windscreen, and an adult’s upper leg form hitting the BLE, only one vehicle (a super mini) passed both tests. 

Regarding the bonnet leading edge test, only two vehicles met the test threshold for injury levels sustained to the upper leg form, and these were both cars with low bonnets (small sports car design). This test only tests an adult's upper leg form. To know what really happens in crashes, crashes need to be fully investigated but given the variability in bonnet leading edge height, high bonnet leading edges would be likely to hit a head or upper body of a child or small adult. No such testing of those body parts is carried out against the bonnet leading edge. Compulsory testing of bonnet leading edges would be likely to lead to manufacturers having to fit softer materials to bonnet leading edges that deform, or external air bags. 

Regarding the windscreen test, more than half (54%) vehicles tested failed. [10] While more than half models submitted to the monitoring-only windscreen test failed it, nearly half passed it, demonstrating that it is possible for manufactures to meet the test’s requirements. Given windscreens are such a danger area, this test is particularly important.

A pillar testing, not currently part of EU regulations, would be likely to result in manufacturers being required to "do something" about A pillars being so hard, with the likelihood that manufacturers would have to fit external airbags in order to pass such a test. 

Tests can also be carried out at higher speeds than currently. For example, the European voluntary windscreen test speed is 35 km/hour. It has been estimated than just over half pedestrians suffer head injuries at impact speeds below 40 km/h but frequency increases to 85.3% at speeds above 40 km/h [11]. This estimation also emphasises the vital importance of slow speeds

It's complicated. Let's summarise 

  • Vehicles and VRUs should be segregated, with separate paths for people on foot, bicycles and motorbikes.
  • Crashes with VRUs should be fully investigated, so we know how vehicles and VRUs collide and injury outcomes. 
  • As a bare minimum, all countries need to adopt UN Regulation 127 or an equivalent, and its requirement for new models sold in those countries to have dummy body parts crashed against bumpers and bonnets and meet the stipulated thresholds.
  • More crash test regulations need to be adopted by the UN, testing dummy heads against the windscreen, A pilllar, and testing various body parts against the bonnet leading edge. Countries need to sign up to these new test regulations as they are set.
  • Tests need to be carried out at 40km/h or higher, and roads where people live should have low speed limits.  

References: 
[1] OECD ITF, Road Safety Annual Report 2016
[2] Chart 2: Casualty and fatality rates per billion passenger miles by road user type: GB, 2014, Reported Casualties Great Britain, June 2016
[3] Dietmar, O., Birgitt, W. (2012) Comparison of Injury Situation of Pedestrians and Bicyclists in Car Frontal Impacts and Assessment of Influence Parameter on Throw Distance and Injury Severity.
[4] R Cookson, R Cuerden, D Richards, J Manning, TRL, A review of the causes of fatal pedestrians’ injuries resulting from collisions with car fronts – comparing vehicles registered in 2002 or later with earlier models, IRCOBI Conference 2009
[5] TRL, Study 26
[6] R Cookson, R Cuerden, D Richards, J Manning, TRL, A review of the causes of fatal pedestrians’ injuries resulting from collisions with car fronts – comparing vehicles registered in 2002 or later with earlier models, IRCOBI Conference 2009
[7] TRL, Study 26
[8] ACEA, 2015
[9] EC, Hynd, D. et al, Benefits and feasibility of a range of technologies and unregulated measures in the field of vehicle occupant safety and protection of vulnerable road users: final report, 2015
[10] ibid
[11] Dietmar, O., Birgitt, W. (2012) Comparison of Injury Situation of Pedestrians and Bicyclists in Car Frontal Impacts and Assessment of Influence Parameter on Throw Distance and Injury Severity

 

 

 

 

 

 

 

 

 

 

It is possible to construct BLEs in ways that are more forgiving to heads. This can be achieved through use of materials that deform easily under pressure, displacing the head into the structure of the vehicle, rather than hard materials that cause the head to stop suddenly. The BLE can also be fitted with external air bags.

The EC’s 2015 report says there is a “potential benefit for head, thorax and abdomen protection for children not yet quantified and should be further reviewed in depth, if considered.” [23]

 

 

 


[10] Richard Cuerden, Mervyn Edwards, Matthias Seidl, TRL for European Parliament, Research for tran committee - the impact of higher or lower weight and volume of cars on road safety, particularly for vulnerable users, 2015
[11] Pedestrian Protection Regulation (78/2009)
[12] EC, Hynd, D. et al, Benefits and feasibility of a range of technologies and unregulated measures in the field of vehicle occupant safety and protection of vulnerable road users: final report, 2015
[13] ibid
[14] ibid
[15] ibid
[16] EC, Saving lives: Boosting car safety in the EU, 2016
[17] EC, Saving lives: Boosting car safety in the EU, 2016
[18] EC, Hynd, D. et al, Benefits and feasibility of a range of technologies and unregulated measures in the field of vehicle occupant safety and protection of vulnerable road users: final report, 2015
[19] Dietmar, O., Birgitt, W. (2012) Comparison of Injury Situation of Pedestrians and Bicyclists in Car Frontal Impacts and Assessment of Influence Parameter on Throw Distance and Injury Severity
[20] EC, Hynd, D. et al, Benefits and feasibility of a range of technologies and unregulated measures in the field of vehicle occupant safety and protection of vulnerable road users: final report, 2015
[21] Dietmar, O., Birgitt, W. (2012) Comparison of Injury Situation of Pedestrians and Bicyclists in Car Frontal Impacts and Assessment of Influence Parameter on Throw Distance and Injury Severity
[22] Euro NCAP Pedestrian Testing Protocol December 2016
[23] EC, Hynd, D. et al, Benefits and feasibility of a range of technologies and unregulated measures in the field of vehicle occupant safety and protection of vulnerable road users: final report