Turning the corner


To reduce the number of accidents, the local authority of the province of Arezzo integrated road safety work into the strategic planning process.

In many regions, having access to high-quality accident data cannot be taken for granted. Accident data and supplementary information are the key to proactive road safety work, a fact that Paolo Vadi knows well. For the last six years he has been in charge of the office for sustainable mobility in the province of Arezzo in Italy. Thanks to a cross-regional project, today he has access to meaningful accident data and this year, with PTV Visum Safety, he has become involved with strategic road safety work.

Between 2001 and 2011 the region of Arezzo recorded around 1,200 accidents each year. Roughly 30 of these were fatal. “Yet we are seeing that the requirements of the Italian National Plan for Road Safety and those of the European Community are taking effect,” says Vadi. “Since 2001 the number of accidents resulting in fatalities has fallen significantly.” To achieve more, road safety work has to be taken into consideration at the road infrastructure strategic planning stage. Before now the most regulating measures would have been decided reactively, which is entirely the wrong approach for Vadi. He was looking for an innovative approach and found it in the form of new technology with
PTV Visum Safety.


In PTV Visum Safety, dangerous roads and junctions are exposed by Heat Maps.

In the first step of its analysis, the province of Arezzo created an initial overview of the data: PTV Visum shows heat maps that indicate whereabouts in the road network the critical points are. Locations with a particularly high accident rate are shown in red. Different filters and settings can be used to further differentiate this view and to configure it according to specific accident categories. The province of Arezzo followed this multi-stage approach. The result was a list of the top 100 black spots, which can be employed in Black Spot Management (BSM).

Focussing on the black spots
One junction in particular stood out when identifying the critical black spots. This location was then analysed in more detail. Factors that encourage accidents were evaluated in order to discover the possible causes of the accidents. Head-on collisions and head-on/side collisions turned out to be the main type of accident at the junction, which is controlled on a fixed-time basis. “Our analysis showed that the reason for the high rate of accidents was certain left-turning drivers disobeying the rights of way,” explains Vadi. “Our primary method of solving the situation was to convert the light signals from three phases to four. By safeguarding turning traffic we promised ourselves a reduction in the accident rate.” Then both the current situation and the new scenario were simulated in PTV Vissim in microscopic detail. In so doing, the region of Arezzo could check the feasibility of the measures while at the same time avoiding potential traffic jams. Vadi’s conclusion: “With this new approach, we hope to be able to significantly reduce the time from an accident black spot emerging to the mitigating measures being put in place on the street.”