The number of deaths and serious injuries among pedestrians hit by cars could be reduced by a novel bonnet design.
Crash specialist Cellbond, based in Huntingdon, Cambridgeshire, has collaborated with researchers at Anglia Ruskin University’s Engineering Simulation Analysis and Tribology (EAST) group to develop and test a prototype.
Pedestrians account for 20 per cent of all traffic fatalities in Europe and 14 per cent in the US — with the majority being caused by head impacts. Statistically, 65 per cent of pedestrians who impact or roll on the bonnet of a car that is going more than 40mph are killed or suffer serious injury.
In such a crash the pedestrian is initially impacted by the car and then by the ground, and most fatalities and head injuries occur when there is insufficient clearance between the bonnet and stiff underlying engine components.
‘Manufacturers are packaging vehicles a lot more compact in order to make them as light as possible. In recent vehicle designs the bonnet is very close to the engine block, so the bonnet acts like a brick wall,’ said Prof Hassan Shirvani, director of Anglia Ruskin University’s EAST group.
There have been attempts to mitigate this through so-called active deployable systems that literally pop up on impact to increase the gap between the bonnet and engine block. Jaguar has such a system in its recent XK models.
However, Cellbond’s design differs in that it is based on a passive approach, using the gap between bonnet and engine block more efficiently to absorb kinetic energy.
‘The bonnet preserves the global stiffness but also localises the load when it’s applied on it. So when the bonnet is hit by the head it deforms locally and absorbs a huge amount of energy before it reaches that solid part with the engine,’ said Dr Mehrdad Asadi, the engineer at Cellbond who headed the project.
This is achieved using a three-layered design comprising an inertia absorber sandwiched between aluminium sheets with a specific etched geometrical-grid pattern, which was devised in computer simulations.
The patented Cellbond car bonnet design has now been tested and verified in a EuroNCAP-certified test house.
The majority of car test standards and protocols use the ‘Head Impact Criteria’ to measure the severity impact on human heads and to restrict the criterion to certain numbers.
Test results show that Cellbond’s design reduced the ’Head Impact Criteria’ by 50–60 per cent compared with standard bonnets.
Shirvani revealed that a ‘major motor manufacturer’ will be using the bonnet in its next generation of models.
I have a Jaguar XFS and I have heard that if you hit a dog or a badger at around 15mph, the Pedestrian Friendly Bonnet sytem will activate.
All very well but Jaguar will charge you £1,200 to reset it !
The Cellbond system sounds like a good idea..
I seem to recall that my Vauxhall Viva 1300 had enough room around the engine to house a small family. Today’s cars in comparison seem to have one solid block filling all crevices under the bonnet. Surely efficient packaging isn’t just cramming as much as possible into as small a space as possible; but rather meeting all criteria including desirable clearances?
Question – is this kind of accident a major issue?
Question – Does this bonnet deform at high speeds?
It is a major concern to look at. A high percentage of pedestrians (60%) who roll on the bonnet of a car that is going more than 40mph are killed or suffer sever injuries.
Regarding to the second question, a little more details please (under what impact conditions, speed…)
Theorectically speaking, it would be more beneficial if all pedestrians would wear Crash helmets and Body Armour.
This would dramictically reduce the number of serious injuries sustained leading to reduced demands on the medical services which in turn would lead to more medical facilities being free for non accident treatment.
If you will pardon the pun, this could be called the “knock-on” effect !
Surely moving the engine to the rear of the car as standard, then having the boot at the front, (like a small number of cars out there), would negate all of this. It’s not often a driver would carry something so solid as a engine in the front boot?
@ anonymous,
while your comment is a valid point, putting the engine at the front has distinctive safety features regarding roadholding and traction which more than outweigh pedestrian safety functions.
Interestingly, a test carried out in Germany a couple of years ago proved that fitting Bullbars to Offroad vehicles actually resulted in fewer injuries to pedestrians, contrary to expected results.
As far as road safety goes the introduction of 20 MPH zones must have had an “Impact” on the pedestrian fatalities.
Keep pedestrians and fast moving traffic a part, surely it is common sense to segregate them and enforce lower speed limits in towns and villages, and to make the highways go round them – seems to work in Holland and Germany
Interesting Topic. I’m working on the Pop-up Bonnet mechanism.
With the Bonnet designed to be doformable is exellent. However the biggest challenge engineering would face is the package space for the engine compartment.
As stated, modern vehicles are very compact in the engine bay area so quite a challenge to create some significant clearance between engine bay hard points and Bonnet.
It can be a good idea to have a pop up Bonnet with Deformable Bonnet stucture somehow incorporated together.
Any comments?
I’m sure the Mazda RX8 had a similar geometric design in an aluminium bonnet for exactly this reason. I do remember the pedestrian friendliness of this innovation being a big marketing thing for them back in 2003. Of course, the snall size of the Wankel engine and it’s low and rearward positioning helped create the space for the bonnet to deform without resorting to pop-up mechanisms.
The problem with the pop bonnet is anything can set it off ie small dog, cat, football, speed bumps. Jaguar then charges £2500 to reset it because you have to replace everything including the bonnet (gets warped)