In-vehicle speed adaptation - On the effectiveness of a voluntary system

The overarching aim of this thesis is to study the long term effects of a voluntary speed adaptation system, the Active Accelerator Pedal (AAP), and its effectiveness for different driver types. The papers making up this thesis are based on a study carried out on 284 vehicles and drivers in the Swedish city of Lund from 1999 until 2002. The results showed that the AAP brought a significant reduction in both mean speed and speed variance, estimated to lead to a reduction in injury accidents of up to 25 % if all vehicles where equipped with the system. It was further found that drivers’ behaviour towards other road users improved, they showed a more correct yielding behaviour and were more likely to give pedestrians the right of way at zebra crossings. Moreover, the time gap to the vehicle in front increased slightly with the system. However, there were also signs of negative behavioural modifications in the form of drivers’ forgetting to adapt their speed to the speed limit when not supported by the system; this effect was not statistically significant though. These positive results augur well for in-vehicle speed adaptation, but this thesis found that the drivers in favour of the AAP were already without it driving at, or close to, the speed limit while those most negative to the system were the fastest drivers. It was further found that the speed-reducing effect of the AAP was lower for those who were negative to the system. The conclusion is that a voluntary system like the AAP will reduce inadvertent but not deliberate speeding. For such a system to reach its full potential, either peoples’ intentions have to be changed or the system has to be more intrusive, i.e. a mandatory limiting system

SPEED REGULATION BY IN-CAR ACTIVE ACCELERATOR PEDAL

The effects on speeds and speed distribution were studied in a large scale field trial with an in car system for speed adaptation in the city of Lund, Sweden. In the trial 290 vehicles were equipped with an "active accelerator pedal" and data logger for a period of 3-11 months. Data was logged in each test vehicle during the whole trial and was analyzed for 3 one-month periods: Before activating the system, after short time use and after long time use. The results showed significant reductions in the speed level. Speeds on stretches decreased statistically significantly (p"0.05) at 60 out of 69 observed sections. The effects were largest on arterial roads, at mid-block sections, where the prevailing traffic conditions and street design allows higher speeds. The standard deviation decreased on all arterial roads, mainly due to the decrease in speed of the fastest vehicles but there is also an effect from an increase in speed of the slowest vehicles. On streets with mixed traffic no differences in speed or speed distribution could be shown. This is most likely due to the fact that speeds were already controlled by the prevailing traffic conditions and they already were so low that the system never had to interfere. Further research is needed in order to investigate possible behavioral adaptation effects when the system is active as well as inactive and how driver behavior would be influenced in a situation where a large part of the vehicle fleet equipped with an active accelerator pedal. (Less) Document type: Articl

Would those who need ISA, use it? Investigating the relationship between drivers' speed choice and their use of a voluntary ISA system

Intelligent Speed Adaptation (ISA) is one of the most promising new technologies for reducing the prevalence and severity of speed-related accidents. Such a system could be implemented in a number of ways, representing various "levels of control" over the driver. An ISA system could be purely advisory or could actually control the maximum speed of a vehicle. A compromise would be to introduce a system that allows a driver to choose when to engage ISA, thus creating a “voluntary” system. Whilst these voluntary systems are considered more acceptable by drivers, they will not offer safety benefits if they are not used by the driver. Two studies were carried out that examined the relationship between drivers’ reported and actual speeding behaviour, their propensity to engage a voluntary ISA system and their attitudes towards such a system. These studies were carried out in a driving simulator and in an instrumented vehicle. In both the studies, drivers’ propensity to exceed the speed limit was lowered when ISA was available but this effect was confined to the lower speed limits. In general, drivers engaged ISA for approximately half of their driving time, depending on the speed limit of the road and indeed, on the nature of the road and the surrounding traffic. This was particularly true in the field study where drivers were more inclined to “keep up with” the surrounding traffic. The results from the on-road study indicated that those drivers who considered ISA to be both a useful and pleasant system, were overall more likely to engage it. However, those drivers who confessed to enjoying exceeding the speed limit were less likely to use ISA. This is an important finding when considering the mechanisms for implementing ISA: those drivers who would benefit most would be less likely to use a voluntary system

Could Intelligent Speed Adaptation make overtaking unsafe?

This driving simulator study investigated how mandatory and voluntary ISA might affect a driver's overtaking decisions on rural roads, by presenting drivers with a variety of overtaking scenarios designed to evaluate both the frequency and safety of the manoeuvres. In half the overtaking scenarios, ISA was active and in the remainder ISA was switched off. A rural road was modelled with a number of 2 + 1 road sections, thus allowing drivers a protected overtaking opportunity. The results indicate that drivers became less inclined to initiate an overtaking manoeuvre when the mandatory ISA was active and this was particularly so when the overtaking opportunity was short. In addition to this, when ISA was activated drivers were more likely to have to abandon an overtaking, presumably due to running out of road. They also spent more time in the critical hatched area - a potentially unsafe behaviour. The quality of the overtaking manoeuvre was also affected when mandatory ISA was active, with drivers pulling out and cutting back in more sharply. In contrast, when driving with a voluntary ISA, overtaking behaviour remained mostly unchanged: drivers disengaged the function in approximately 70% of overtaking scenarios. The results of this study suggest that mandatory ISA could affect the safety of overtaking manoeuvres unless coupled with an adaptation period or other driver support functions that support safe overtaking

An Ontological Approach to Inform HMI Designs for Minimizing Driver Distractions with ADAS

ADAS (Advanced Driver Assistance Systems) are in-vehicle systems designed to enhance driving safety and efficiency as well as comfort for drivers in the driving process. Recent studies have noticed that when Human Machine Interface (HMI) is not designed properly, an ADAS can cause distraction which would affect its usage and even lead to safety issues. Current understanding of these issues is limited to the context-dependent nature of such systems. This paper reports the development of a holistic conceptualisation of how drivers interact with ADAS and how such interaction could lead to potential distraction. This is done taking an ontological approach to contextualise the potential distraction, driving tasks and user interactions centred on the use of ADAS. Example scenarios are also given to demonstrate how the developed ontology can be used to deduce rules for identifying distraction from ADAS and informing future designs