The value of site-based observations complementary to naturalistic driving observations: a pilot study on the right turn manoeuvre.

Naturalistic driving studies are increasingly applied in different shapes and sizes. The European project PROLOGUE has investigated the value and feasibility of a large-scale naturalistic driving study in Europe. Within PROLOGUE several pilot studies have been conducted in different countries. The Dutch field trial investigated the value and feasibility of adding site-based observations to in-vehicle observations. In this trial, one intersection was equipped with cameras for site-based observation. Additionally eight cars were equipped of drivers crossing this intersection regularly. On this small scale, combining the two observation methods turned out to be technically feasible. It was possible to recognise the instrumented vehicles in the site-based video data, to match cases from the different observations and the speed measures from the separate studies appeared to be similar. The value of combining these two observation methods lies in the possibility to enrich the data from one study with complementary data from the other study. The study illustrated that each type of observation has its unique values. From in-vehicle data it is possible to look in detail at the driving behaviour of the participants over time and in different situations. The site-based study offers information about the position and speed of other road users surrounding the participant's vehicle, including vulnerable road users such as cyclists and pedestrians. Two values of adding site-based observations to in-vehicle observations were identified: to obtain more in depth understanding and to relate the behaviour of participants of the naturalistic driving study to behaviour of the full population of drivers (non-participants). For a future (large-scale) naturalistic driving study two research topics are identified that could benefit from these complementary observations: driving behaviour in relation to specific infrastructure and the interaction between drivers and vulnerable road users.

Driving with a Congestion Assistant; mental workload and acceptance.

New driver support systems are developed and introduced to the market at increasing speed. In conditions of traffic congestion drivers may be supported by a "Congestion Assistant", a system that combines the features of a Congestion Warning System (acoustic warning and gas pedal counterforce) and a Stop & Go system (automatic gas and brake pedal during congestion). To gain understanding of the effects of driving with a Congestion Assistant on drivers, mental workload of drivers was registered under different conditions as well as acceptance of the system. Mental workload was measured by means of physiological registrations, i.e. heart rate, a secondary task and with the aid of subjective scaling techniques. Acceptance was measured with an acceptance scale. The study was carried out in an advanced driving simulator. Driving with the Congestion Assistant while in congestion potentially leads to decreased driver mental workload, whereas just before congestion starts, i.e. developing just noticeable, the system may add to the workload of the driver. Acceptance is generally high after experiencing the system, though not in all respects.