The project ‘Het Slimme wegdek’ (The intelligent road surface) is part of the programme ‘Wegen naar de Toekomst’ of the Dutch Ministry of Transportation, Public Works, and Water Management. Two assistance systems for merging at places where a third motorway lane ends were developed by two consortia. Both systems make use of a road surface embedded ‘moving’ LED light line, and information on variable matrix signs (VMS) above the road. In advance of a possible field test, a first estimate was required of effects on behavioural effects, comprehensibility, and acceptance. The Follow Me system has a coarse and a fine adjustment zone. At the coarse zone VMS were used to decrease speed and speed variability, in the fine adjustment zone vehicles in the centre lane were guided by a running LED light in front of each vehicle. In this latter zone lane changing was at first prohibited by continuous dynamic lane marking. Purpose of the LED light following was to facilitate the merge manoeuvre from the left to the centre lane. The ‘Denkdek’ (‘Thinking roadsurface’) also made use of a running LED line, but here the line was embedded in the road surface on the emergency lane. The speed of movement of this line was not tuned to individual vehicles (as was done in the Follow Me system), but the lines were moving at a pre-set target speed. On the VMS above the road different speed limits per lane were displayed to induce small (5 km/h) speed differences, which should facilitate merging. Traffic on the centre lane was encouraged to merge to the right-hand lane, and in this way create gaps on the centre lane. Traffic from the left-hand lane should make use of these gaps and merge to the centre lane. In the TNO Human Factors driving simulator, the ‘Follow-Me’ system was evaluated, and at the Department of Psychology of the University of Groningen the ‘Denkdek’ was evaluated in the driving simulator. Both systems were implemented in the driving simulators on the basis of specifications provided by the consortia. Participants made a total of 25 test rides, both with and without the system switched on. All other traffic obeyed to the system as the ideal situation described by the consortia. Both systems reduced speed, the Follow Me system in particular on the centre lane in the fine adjustment zone where large decelerations were measured. TTC values at the moment of merging shifted towards critical values, but this did not lead to any conflicts. On the Denkdek drivers decelerated more spread over the 1 km length test track. With this system switched on more traffic merged from the centre to the right-hand lane. Mental effort was higher when driving on the centre lane with the Follow Me system switched on. Ease and smoothness of the manoeuvre were judged to be less compared with the situation where the system was switched off. A similar effect was found with the Denkdek: rides with the system switched on were more effortful, and less easy. An important group of participants (28%) reported to have ignored the system, and 41% is afraid that the system will draw away attention from the rest of the traffic. Acceptance of both systems was neutral to slightly positive. Operational application of the Follow Me system in its present form is not advisable. It is recommended to first improve the system by: (1) find more thorough basis for the algorithm by using real traffic data on an individual vehicle level, (2) microscopic traffic simulation, (3) additional driving simulator experiments, (4) a field trial in a highly- controlled environment. For Denkdek, no objections against operational application appeared in terms of behavioural effects. However, one needs to be aware of potential distraction of the system. Even though self-reported mental effort was not dramatically increased, one out of four participants said to have ignored the system. (Author/publisher)
Samenvatting