Novel Safety Requirements and Crash Test Standards for Light- Weight Urban Vehicles

University essay from KTH/Lättkonstruktioner

Author: David Egertz; [2011]

Keywords: ;


In recent years the interest for smaller, cheaper and more energy efficient vehicles hasincreased significantly. These vehicles are intended to be used in urban areas, where theactual need of large heavy cars is generally minor. The travelled distance is on average lessthan 56km during a day and most often there is only one person travelling in the vehicle. Manyof the established car manufacturers have recently started to take interest into this marketsegment, but the majority of these small vehicles are still manufactured by smaller companiesat a low cost and with little or no research done on vehicle traffic safety. This may be becausethere are still no legal requirements on crash testing of this type of vehicles.This report will examine road safety for Urban Light-weight Vehicle (ULV) to find criticalcrash scenarios from which future crash testing methods for urban vehicles can be derived.The term ULV is specific to this report and is the title for all engine powered three- and fourwheeledvehicles categorized by the European Commission. Other attributes than the wheelgeometry is engine power and the vehicles unladen mass. The maximum allowed weight for athree-wheeled ULV is 1 000kg and 400kg for a four-wheeled one.By studying current crash test methods used in Europe by Euro NCAP it has beenconcluded that these tests are a good way of assessing car safety. For light-weight urbanvehicles it has been concluded that some of these tests need to be changed and that some newtest scenarios should be added when assessing road safety. The main reasons for this is linkedto that vehicle’s with a weight difference of more than 150kg cannot be compared withcurrent test methods, and that crash tests are performed with crash objects with similar orequal mass in current safety assessment programs. This correlates poorly to the trafficsituation for light-weight urban vehicles since it would most likely collide with a far heaviervehicle than itself in an accident event.To verify the actual traffic situation in urban areas, accident statistics have beenexamined closely. The research has shown that there are large differences between rural andurban areas. For instance; 66% of all severe and fatal traffic accident occurs in rural areaseven though they are less populated. Even the distribution of accident categories has showndifferent in rural and urban areas. The United Nations Economic Commission for Europe(UNECE) has defined accident categories in their database which is widely used within theEuropean Union. By comparing each accident category’s occurrence, injury and fatality rate,the most critical urban accident categories were found in the following order.

1. Collision due to crossing or turning

2. Vehicle and pedestrian collision

3. Rear-end collision

4. Single-vehicle accident

5. Other collisions

6. Head-on collision

Statistics also show that of all fatally injured crash victims in urban trafficapproximately; one third is travelling by car; one third by motorcycle, moped or pedal-cycle;and one third are pedestrians. This means that unprotected road travelers correspond to twothirds of all fatal urban traffic accidents, a fact that has to be taken into account in future crashtesting of urban vehicles. With all the information gathered a total of four new crash testscenarios for light-weight urban vehicles have been presented:

• Vehicle-to-vehicle side impact at 40km/h with a 1 300kg striking vehicle to evaluate theoccupant protection level of the light-weight vehicle.

• Vehicle-to-motorcycle side impact at 40km/h with motorcycle rider protection evaluation.

• Pedestrian protection assessment at 40km/h over the whole vehicle front and roof area.

• Rigid barrier impact at 40km/h corresponding to an urban single vehicle accident with aroad side object or a collision with a heavier or similar sized vehicle.

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