Potential of heavy goods vehicle countermeasures to reduce the number of fatalities in crashes with vulnerable road users in Sweden

Background

The Swedish parliament adopted Vision Zero in 1997 and has since then reduced road fatalities by approximately 60%. Sweden had in 2020 a fatality rate of 19 road fatalities per million population and year (Hurtig et al., 2023). Together with Norway, this is the lowest traffic fatality rate in the world. Vision Zero acknowledges that is in the human nature to make errors, mistakes or misjudgements and aims at aligning the crash severity with the potential to protect from bodily harm. This facilitates an environment where crashes involving safe vehicles, safe infrastructure, safe speed and safe road users won’t result in fatally or severely injured individuals. Using the Vision Zero approach (Larsson & Tingvall, 2013), one would design specific road elements (roads, vehicles etc.) anticipating the speeds of vehicles and types of crashes that road users could experience.

While Heavy Goods Vehicles (HGVs; Gross Vehicle Weight Rating > 3.5 tonnes) make up 6% of vehicle mileage in Sweden (Trafikanalys, 2024), these vehicle types have been involved in 15-20% of road fatalities in the last decade (Hurtig et al., 2023). The high involvement of HGVs in fatality crashes is not restricted to Sweden. A European research project reported that HGVs were involved in 14.2% of road fatalities in 2015 even though the total involvement rate was only 4.5% of all road collisions (Schindler et al., 2018). A study of Swedish HGV crashes for the years 2012-2021 identified a total of 455 fatalities. The deceased individuals in these crashes were, in almost all cases (92%), the collision partner of the HGV (Thomson et al., 2023). Several studies examined collisions with fatal and serious injury outcomes between HGV/pedestrians and HGV/cyclists collected from polis reports and insurance company (Christie et al., 2015; Malczyk & Bende, 2019; Talbot et al., 2017). Patterns identified for HGV/cyclists’ collisions occurred at junctions where the HGV was turning right or left for left-driving countries. For collisions between HGV and pedestrians, they mostly occurred during stationary and moving-off scenarios in front of the truck. Authors agreed that those scenarios occurred in complex situations which require multiple countermeasures to prevent them. It was concluded that the improvement of truck driver’s visibility of the cyclists on the right side of the HGV and of the pedestrians in the near front would be a potential countermeasure.

After having focused on passenger car safety to a great extent, regulators have acknowledged this road safety issue. The General Safety Regulation (GSR) update includes several areas relevant for HGV, including e.g. speed assistance systems, Advanced Emergency Braking for Vulnerable Road Users (VRUs) in 2028 for new registrations and driver distraction in 2026 (GSR, 2019; GSR, 2021). Further, the European consumer test programme, Euro NCAP, has published a road map (EuroNCAP, 2023) detailing plans to launch consumer tests of heavy commercial vehicles in three phases starting in year 2024. In the first phase, active safety countermeasures will be evaluated since it is believed to be most feasible to introduce on a short-term. Mid-term, year 2027, driver attention assessment is planned, including driver monitoring of distraction and drowsiness. Longer-term, in year 2030, assessment of passive safety for HGV occupants and compatibility with other motor vehicles and vulnerable road users are planned.

While the road map is already quite detailed on an overall level, the specific test scenarios and their respective scoring still need to be decided. In order to support that process, further crash analysis is very valuable, to understand these scenarios in detail, as well as how potential countermeasures can be effective. As a first step, the present study focusses on fatalities among VRUs in collision with an HGV.

Aim

The aim of the study was to evaluate existing and future HGV countermeasures with respect to their potential efficiency to save lives among VRUs (i.e. GSR and coming Euro NCAP for HGV). As vehicles are part of the transport systems, the safe system approach is adopted here. Thus, HGV safety systems were prioritised to study their potential to avoid fatalities, which can be a prevented collision or mitigation of injury severity. The results will be used for understanding the potential of the included countermeasures and what the contribution to reduced fatalities in the transport system these may have.

Method

Results

Discussion

The aim of the study is to evaluate existing and future safety systems on HGV regarding their potential efficiency to save lives among VRUs. In total, 63 fatal crashes were studied from a system perspective by retrospectively analyzing the entire time frame leading to fatalities. The majority of the fatalities are pedestrians, followed by PTW riders and bicyclists. Crash pattern for each VRU type is specific, namely, moving-off scenarios for pedestrians, frontal collision and HGV turning left for PTW, and HGV turning right for bicyclists. Active safety systems were found to potentially address the majority of those scenarios. Patterns identified and countermeasures regarding improved truck drivers' vision of VRU on the right side of the truck and in the near front area are also find in the present study (Christie et al., 2015; Malczyk & Bende, 2019; Talbot et al., 2017). More specifically, we could identify a large potential to save pedestrians lives with MOIS and direct vision and bicyclists lives with AEB junction and BSIS. Passive safety systems have also a large potential. This study especially showed the need for protecting pedestrians and bicyclists from being run over by the heavy goods vehicle. The flat vertical design of the front is likely to contribute to this compared to a passenger car where a pedestrian or bicyclist typically lands on the hood and travels with the vehicle during part of the crash decreasing the risk of sliding down under the vehicle. This study also showed the need to further develop designs to prevent bicyclists from under-running the side of the heavy goods vehicle. The current regulatory side protection (UNECE R73) was evaluated to understand if the severe outcome in a crash was mainly due to the existing exceptions in the regulation (tractors for semi-trailers and special purpose vehicles), or failure to follow regulation, or if additional countermeasures were needed to modify the outcome in the crashes, which was found to be a potential candidate in the extended side protection countermeasure (UN/ECE, 2011). Similarly, VRU protection (as regulated by UNECE R61) was included to keep the consensus group aware of any illicit HGV modifications, which potentially could have made the crash more severe (UN/ECE, 1984). However, no indications of such modifications were identified. Although this study did not show potential effect for passive pedestrian protection (energy absorption), this could partly be due to the limited sample size of the study. Also, this could be hidden by the fact that many were over-ridden by the HGV which creates more severe injuries. If this is solved, the passive pedestrian protection issue may very well rise to the surface. Furthermore, both active and passive systems were found to complement each other, adding robustness or redundancy in a crash. Although it is often difficult for active safety systems to reach full avoidance, they can often reduce impact speeds down to levels where it is easier to protect with passive safety systems. Speed was found to not be an issue neither for HGV nor for pedestrians and bicyclists. However, speed was found to be a major contributor in PTW crashes where the high speed of the motorcycle was considered outside of effective boundaries for the safety systems included. Driving under the influence of alcohol for HGV drivers was not found to be a relevant factor in the studied crashes, as no drivers tested positive for alcohol.

The safe system approach, where all parts of the transport system are integrated, is needed to prevent all crashes and injuries, i.e. HGV systems, PTW systems, VRU systems, infrastructure, connected systems, etc. However, as a first step, the focus was to evaluate the potential of HGV countermeasures. The list of countermeasures was designed based on current and potential future HGV safety systems relevant to all or individually targeted VRU groups but not brand specific. The safety systems included here are not conclusive, but a selection based on potential effect of present or coming systems. In addition, some of the passive safety systems are custom variants of existing countermeasures where no specific limitations for actual implementation possibilities are proposed, but rather a system included to identify an area of improvement, e.g. the different extended underrun protection systems and wheel protection. Regarding the effect of the systems included, independently the level of automation, all systems were considered to have a 100% effectiveness where the boundary conditions were met, which means that adverse weather conditions and possible misusage or behavioral adaptation where not included. Thus, it is likely that warnings are less effective than automatic vehicle-induced interventions since warnings may be neglected or misunderstood by the driver.

The countermeasure definitions and boundaries are simplified and loosely based on system descriptions in the European GSR and in the coming HGV protocol for Euro NCAP testing. The functionality interpretations are set at a low stringency level to allow for hypothesis testing against the data available in the STA database. In many cases, there is no information on travel speed for the HGV, and for the VRU no speed is available at all. The speed estimation of VRU was based on the findings in Wisch et al. (2013), and the expertise from the consensus group.

The potential for saving lives of active and passive systems on HGV seems to be promising in the light of the present results. However, to get closer to the halving of fatalities by 2030 and Vision Zero, there will be a need to implement other types of countermeasures such as infrastructure, systems on PTW or on bicycle. As emphasized by previous research, collisions between HGV and VRU are complex and require a multiple approach to prevent then (Talbot et al., 2017). Moreover, education and enforcement of legislation were not included in the present study, but they already have a documented effect in PTW crashes (Forsman et al., 2021). In PTW scenarios, there is a large potential for saving lives with coming connected safety systems. The future systems will support both the PTW riders and the HGV drivers to increase their awareness and perception that a vehicle, not visible, will soon be in a collision angle and preventive actions need to be taken such as decrease speed or stay in your lane until the approaching vehicle has passed. In the present study, seven fatalities could have been prevented by connected safety systems, giving an overall theoretical reduction of 70% of fatalities.

Utilizing the Safe System approach and having a holistic mindset to manage HGV crashes, the available safety technologies need to be deployed to a broad extent to save the maximum number of lives. The penetration rate of safety technology is limited in Europe. With an average age of trucks of 14.2 years in the EU (ACEA, 2023), a broad effect of safety systems will not be a reality before many years. The upcoming regulations in Europe, as well as the introduction of consumer rating tests, will most likely contribute to increase the penetration of safety systems on the market and will accelerate the decrease of fatalities in traffic. Additional in-depth studies in other regions of the world where data is available and studies including light and severe injuries are urgently needed to deliver relevant data for several stakeholders to act on the situation to reach the goal of halving fatalities by 2030 worldwide.

Conclusions

Based on the study results, the following could be concluded:

• Countermeasures regarding improved truck drivers' vision of Vulnerable Road Users (VRUs) on the right side of the truck and in the near front area are found to be effective to save lives.

• Large potential to save pedestrians lives was found with Moving Off Information Systems (MOIS) and direct vision.

• Large potential to save bicyclists lives was found with Advanced Emergency Braking system (AEB) junction and Blind Spot Information System (BSIS).

• There is a need for protecting pedestrians and bicyclists from being run over by the wheels of a heavy goods vehicle.

• Both active and passive systems were found to complement each other, adding robustness or redundancy in a crash.

• Upcoming regulations in Europe, as well as the introduction of consumer rating tests, will most likely contribute to increase the penetration of safety systems on the market and will accelerate the decrease of fatalities in traffic.

Declaration of competing interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Availability of data

All data supporting the article could be accessible through application at the Swedish Transport Administration.

Funding

The present work has been funded by the two main organisations namely Volvo Group Technology and the Swedish Transport Administration.

CRediT contribution statement