Assessment of the use of the emergency lane in Morges
© Alain Herzog 2014
After four years of implementation, EPFL researchers have found that the partial opening of the highway’s emergency lane in Morges has major effects on the route’s traffic flow. They have also suggested some tips for the improvement of this system.
It is known as an active emergency lane; that is: an emergency lane temporarily open to traffic. Since January 2010, this is the case for a four kilometers stretch between Morges and Ecublens. Its goal is to smooth the traffic flow of, at rush hour, 82’000 daily vehicles traveling on the A1 Lausanne-Geneva highway. Does it really work? Researchers from the Traffic facilities laboratory (LAVOC) at EPFL have assessed the effectiveness and impact of this measure. They have found that it undoubtedly decreases congestion and accidents, but they also believe that some modifications would bring about an optimal result.
The most notable effect of this active emergency lane is the intensification of the traffic flow: there has been an increase of approximately 750 vehicles per hour over a total of approximately 6’000 vehicles, despite a lower speed limit of 100 km/h instead of 120 km/h. Regardless of this increase in traffic, "simulations show that this represents a reduction of one-fifth of CO2 emissions due to smoother traffic and reduced speed," said Professor André-Gilles Dumont, head of LAVOC.
However, the effectiveness of this measure often comes down to a matter of minutes. When the flow reaches 35 vehicles per km, an alarm is triggered at a checkpoint at Blécherette. An employee must manually enable the opening of the lane. Still, sometimes it only takes a few minutes for the formation of a traffic jam which then takes some time to be dissolved. "We seek to integrate other parameters apart from the flow to determine the opening of the system: the vehicle distribution by lane or the speed differences among the lanes. The most important thing is to maintain the flow of traffic as it is very difficult to recover it once a traffic jam is in place," said the professor.
A better signaling
As for accident prevention, a more responsive system would also improve the situation. The introduction of the active emergency lane has resulted in an overall decrease of a quarter of the number of accidents that occurred between 2008 and 2013. "They are often related to lane changes. If we want to reduce them, it is essential for drivers entering the highway to know as soon as possible that the lane is open so that, for example, they stay on it as long as possible", said André-Gilles Dumont.
Surveys conducted by researchers two years after the start of the system also showed that the measure was not yet fully adopted by drivers. Nearly 70% of respondents did not hesitate to use it. However a fourth of them felt uncomfortable to cross the white line and the same proportion did not feel safe.
To remedy this, scientists recommend a better signaling. "A kilometer before entering the highway, in this case at Aubonne and at Crissier, it would be necessary to place a sign indicating whether the emergency lane is open or closed," said the professor. In addition, the study suggests indicating each lane’s speed limit in the section where the emergency lane is open. Currently, there are only two speed limit signs on gantries that are thus placed between the lanes. Meanwhile, scientists are thinking about a specific sign to allow drivers to pass across the white line with less apprehension.
Other highway sections under consideration
Conducted since 2011, the study provides new prospects for the future. In collaboration with other two EPFL laboratories, researchers have also carried out a study on driver behavior through the use of drones. When do drivers change lanes? Under what conditions? What paths do they take? The flights to conduct the investigation took place in March 2014. The analysis of this exploratory study is still underway.
The assessment of the partial opening of the emergency lane in Morges is particularly relevant as other Swiss highway sections could use a similar system. That will be the case in 2015 in the Bern region between the Berne-Wankdorf and Muri intersections. There are also plans for its development at the entrance of Geneva, between Nyon and the Vengeron intersection as well as between the Cossonay junction and the Villars-Sainte-Croix intersection.
The Traffic facilities laboratory (LAVOC) was commissioned by the Fund for road research (Fonds pour la recherche routière) to carry out this study. It collaborated with the Geodetic engineering laboratory (TOPO) and the Computer vision laboratory (CVLAB).
