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Emergency braking

Based on radar (short and long range), LIDAR and/or camera vision, emergency braking support systems provide support in situations with a high risk of a head to tail collision in order to avoid the collision or to reduce the collision speed and the total crash energy. Total crash energy reduction correlates directly to crash injury mitigation. Different levels of support are available: enhancement of driver’s braking if necessary, automatic activation of partial braking, and automatic activation of full braking. Some systems also trigger reversible measures of occupant protection.

Emergency braking improves safety by reducing crash speeds and thereby crash energy or even by preventing crashes altogether. The system reduces and mitigates specifically rear-end crashes, and collisions with pedestrians and fixed obstacles. The system is estimated to reduce the overall fatality and injury risks by 7%. The effects on emissions and fuel consumption, due to reduced crash originated congestion, are estimated to be positive but small.

Results Methods Author(s) Year Publication details
Autonomous emergency braking was estimated to reduce the number of rear-end accidents by 38%. The results are based on analysis of real-world accident data with a meta-analysis approach combined with the induced exposure method. The study involved analysis of accident data in six countries of which most were located in Europe. Fildes, B., Keall, M., Bos, N., Lie, A., Page, Y., Pastor, C., Pennisi, L., Rizzi, M., Thomas, P., Tingvall, C. 2015 Effectiveness of low speed autonomous emergency braking in real-world rear-end crashes. Accident Analysis & Prevention, Volume 81, pp. 24-29
According to a preliminary benefit estimate of NHTSA, a system including forward collision warning, dynamic brake support and crash imminent braking functionalities will reduce the number of fatalities by 100 and the number of serious injuries by 4,000 in the US, if installed in all light vehicles. The reduction in injuries and fatalities was estimated by combining the expected reduction in collision speed for various types of accidents achieved with the system with the statistics of police reported accidents in the US. The impact of collision speed on accident severity was estimated with curves available for relations between speed and injury probabilities. US DOT, National Highway Traffic Safety Administration (NHTSA) 2014 Automatic Emergency Braking System (AEB) Research Report. NHTSA, US DOT.
Automatic emergency braking system combined with brake assistant was estimated to reduce fatal pedestrian accidents by 15.3% and pedestrian accidents with serious injury by 38.2% in France. This corresponds to 1.3% of all fatal accidents and 3.8% of accidents with a serious injury in France. This estimate applies to a system with 100% fleet penetration in passenger vehicles and a system with 100% reliability. The results are based on a case-by-case analysis of pedestrian accidents in six European countries. The safety impact has been estimated by assuming that an emergency braking combined with brake assistant results in reduction in the impact speed. The reduction in impact speed was then used to estimate the reduced probability or serious injury in the analysed accident cases. Finally, the results of the case by case analysis were extrapolated to French conditions using French data on pedestrian accidents. The system analysed in the study was assumed to operate with reliability of 100% and be effective for all road types and weather conditions. Chauvel, C., Page, Y., Fildes, B. and Lahausse, J. 2013 Automatic Emergency Braking for Pedestrians Effective Target Population and Expected Safety Benefit.Proceedings of the 23rd Enhanced Safety of Vehicles Conference, Seoul, Korea, 27-30 May 2013.
The analysis showed that drivers allocated their attention towards the roadway and braked immediately after receiving a forward collision warning. After a few seconds after the warning, drivers' eye movements directed away from the roadway towards the source of the warning in the instrument cluster. The results are based on analysis of 60 naturally occurred collision warning events. The study included both baseline and treatment periods (27 valid events during the baseline period and 33 valid events during the treatment period). The data analysed in the paper was collected in naturalistic setting and extracted from the database collected in the EuroFOT project. The analysed data consists of 20 Dutch truck drivers. Wege, C., Will, S. and Victor, T. 2013 Eye movement and brake reactions to real world brake-capacity forward collision warnings - A naturalistic driving study. Accident Analysis and Prevention, Vol. 58, pp. 259-270.(abstract)
The results of forward collision warning were partly inconclusive. However, the results indicated a negative automation effect: the test drivers maintained higher mean speeds with the forward collision warning (with emergency braking) when no unexpected events (such as the lead car braking hard) were present. The results are based on driving simulator tests with 30 participants and statistical analysis of test results. Muhrer, E., Reinprecht, K. and Vollrath, M. 2012 Driving With a Partially Autonomous Forward Collision Warning System; How Do Drivers React? Human Factors: The Journal of the Human Factors and Ergonomics Society October, 2012, Vol. 54, Issue 5, pp. 698-708.
Automatic emergency braking system was estimated to reduce the number of fatalities by 30% in accidents in which the front of the car impacts another vehicle. The result is based on an in-depth analysis of a sample of 100 fatal accidents involving the front of a car impacting another vehicle. Robinson, B., Hulshow, W., Cookson, R., Cuerden, R., Hutchins, R. and Delmonte E. 2011 Cost benefit evaluation of advanced primary safety systems: Final report. Published Project Report PPR586. Transport Research Laboratory, Leeds, UK.
Brake assist system was found to reduce the stopping distance during panic braking on average by 1.43 ft (0.436 m) when braking was initiated at speed of 45 mph (72 km/h). The results are based on test track trials with 64 test drivers. Fitch, G. M., Blanco, M., Morgan, J. F., Rice, J. C., Wharton, A., Wierwille, W. W. & Hanowski, R. J. 2010 Human Performance Evaluation of Light Vehicle Brake Assist Systems: Final Report. U.S. DOT, National Highway Traffic Safety Administration.
Emergency braking system was estimated to reduce CO2 emissions by 0.007% in EU, if the system had 100% penetration in vehicle fleet. The impact of emergency braking system on CO2 emissions was estimated through the reduction in the number of accidents and accident-related congestion. The estimate for the reduction of CO2 emissions is based on the eIMPACT study and assumptions made by the authors. Klunder, G. A., Malone, K., Mak, J., Wilmink, I. R., Schirokoff, A., Sihvola, N., Holmén, C., Berger, A., de Lange, R., Roeterdink, W. and Kosmatopoulos, E. 2009 Impact of Information and Communication Technologies on Energy Efficiency in Road Transport - Final Report. TNO report for the European Commission.
A collision mitigation braking system which is able to collect information about the environment around the vehicle, warn the driver, and perform a braking manouvre could have prevented 17.8% of all accidents involving personal injury in the data sample. The corresponding safety potential of a lateral guidance system consisting of lane keeping assistant and lane change assistant was estimated to be up to 7.3%. It was estimated that a car fleet equipped with both lateral guidance and collision mitigation braking system could have avoided up to 25.1% of all accidents included in the data sample. The results are based on an in-depth analysis of a sample of 2,025 accidents taken from a database maintained by German Insurers Accident Research (UDV). Kuehn, M., Hummel, T. and Bende, J. 2009 Benefit estimation of advanced driver assistance systems for cars derived from real-life accidents. Proceedings of the 21st International Technical Conference on the Enhanced Safety of Vehicles Conference (ESV) - International Congress Center Stuttgart, Germany, June 15–18, 2009.
Autonomous braking systems like Volvo's City Safety have been found to have potential to prevent annually 263,250 crashes, mitigate 87,750 and prevent 151,848 injuries corresponding to savings of 2 million euro in a year in repair costs and insurance claims in the UK if standard fleet wide fitment is assumed. The results are based on data collected on insurance claims, average values of insurance claims and assumptions made by the authors. Avery, M. and Weekes, A. 2009 Autonomous braking systems and their potential effect on whiplash injury reduction. Proceedings of the 21st International Technical Conference on the Enhanced Safety of Vehicles Conference (ESV) - International Congress Center Stuttgart, Germany, June 15–18, 2009.
The emergency braking was found to reduce both fatalities and injuries by 7% in EU25, considering also likely behavioural adaptation effects of the system. The system especially addresses rear-end-collisions and collisions against fixed obstacles. The estimates for the safety impacts are based on synthesis of earlier studies, the power model presented by Göran Nilsson and assumptions made by the authors. Wilmink, I., Janssen, W., Jonkers, E., Malone, K., van Noort, M., Klunder, G., Rämä, P., Sihvola, N., Kulmala, R., Schirokoff, A., Lind, G., Benz, T., Peters, H. and Schönebeck, S. 2008 Impact assessment of Intelligent Vehicle Safety Systems. eIMPACT Deliverable D4, Socio-economic Impact Assessment of Stand-alone and Co-operative Intelligent Vehicle Safety Systems (IVSS) in Europe (eIMPACT)
Emergency brake assist was found to reduce the number of fatalities and injuries by 7.8% and the number of severe injuries and fatalities by 14.6% in case of cars with four stars in Euro NCAP classification. Effectiveness of emergency brake assist in preventing accidents or mitigating their consequences was estimated on the basis of police-reported accident data collected in France for vehicles having four stars in Euro NCAP classification. Cuny,S., Page, Y. and Zangmeister, T. 2008 Evaluation of the safety benefits of existing Safety Functions. TRACE Deliverable D4.2.2.
Brake assistance system reduced rear-end collisions by 8%. The system also reduced the severity of accidents involving pedestrians: the proportion of severe accidents of all accidents involving pedestrians was reduced from 36.4% to 31.7%. The estimates are based on a comparison on the numbers of accidents involving Mercedes Benz vehicles registered in years 1996-1997 and 1997-1998. Brake assistance system was made standard in all Mercedes Benz passenger vehicles in 2007. The accident figures were compared for years 1998-1999 for the former and 1999-2000 for the latter group of vehicles. The figures were compiled on the basis of samples of all accidents reported by the police in Germany. Breuer, J. J., Faulhaber, A., Frank, P. and Gleissner S. 2007 Real world safety benefits of brake assistance systems. Proceedings of the 20th International Technical Conference on the Enhanced Safety of Vehicles Conference (ESV) in Lyon, France, June 18-21, 2007.
A statistically significant 28% reduction in rear-end crashes related to the deployment of the three analysed safety systems was found. However, the largest share of this benefit came from the effect of collision warning system (CWS). The safety effects were estimated using a statistical model and information on the frequency and severity of rear-end conflicts encountered during the field operational test. The field operational test involved a baseline fleet of 20 vehicles, the control fleet of 50 vehicles equipped with a collision warning system (CWS) and the test fleet of 50 vehicles equipped with both CWS, adaptive cruise control (ACC) and electronically controlled brake system (ECBS). Lehmer, M. J., Brown, V., Carnell, R., Christiaen, A-C., McMillan, N., Orban J., Stark, G., Miller, R. and Rini N. A. 2007 Volvo trucks field operational test: evaluation of advanced safety systems for heavy trucks. Proceedings of the 20th International Technical Conference on the Enhanced Safety of Vehicles Conference (ESV) in Lyon, France, June 18-21, 2007.