Joint Road Safety Analysis in Open Roads and Tunnels

1. Introduction

The issue of road safety inspections in tunnel was discussed in two workshops held at the European Social and Economic and Social Committee (EESC) by a group of international stakeholders in February and May 2013: a debate that was initiated about operations such as Road Safety Audit (RSA) during the design process or Road Safety Inspection (RSI) after opening to traffic, according to the prescriptions of the Directive 2008/96/EC (Road Infrastructure Safety Management – RISM). Such operations could be beneficial for risk prevention in tunnels, but the Directive 2008/96/EC does not apply to road tunnels, which are covered by Directive 2004/54/EC (on tunnels safety management): a formal interpretation of the two Directives may lead to a barrier to the safety inspection of the whole infrastructure.

In fact, from the user’s (drivers) point of view, a road is a unique linear infrastructure although it is clear for the driver that such a linear infrastructure consists of open terrain (open roads) and occasionally closed environment (tunnels). The driver wants to receive the same high safety levels, without being interested to know all the details of the ‘infrastructure safety chain’ that produces such safety.

On the other hand, from the infrastructure managers’ point of view, the road is surely not a unique linear infrastructure, because producing and managing safety in a closed environment (tunnels) is much more demanding and extreme than in an open road infrastructure.

Due to different characteristics of a tunnel (e.g. level of visibility, design, enforcement of traffic regulations, etc.), it is important to look at the safety perception of drivers in this environment, otherwise called—subjective safety [1] in normal conditions, as well as in critical scenarios. The users’ perspective was also analysed in 2010 [2], revealing several causes of fear induced to users.

In order to find a common harmonised approach in tunnel and open road safety management, during the year 2016, an international group of road safety experts and tunnel experts visited five road sections with open roads and tunnel in Europe and performed joint safety analyses together with the infrastructure managers in the framework of the European Project ECOROADS [3] (Table 1).

Such analyses were conducted according to a predefined experimental procedure foreseeing the figure of a ‘facilitator’ in charge to maintain the contacts between the group of experts, several external observers, and the infrastructure manager, as well as to ensure an adequate feedback after the visit (Figure 1).

The effectiveness of the joint analyses respect to the usual ones was fully confirmed, and their main aspects related to the definition of the transition area and common check lists are reported in the following sections.

2. Definition of the ‘transition area’

For the scope of the joint safety analysis, the transition area between an open road and a tunnel covers areas both inside and outside the tunnel.

As a minimum requirement, it is intended to be the sum of:

1. The distance calculated as the distance covered in 10 s by a vehicle travelling at the speed limit before the tunnel portal, and

2. the stopping distance inside the tunnel after the portal, for a vehicle travelling at the speed limit, if not identical with design speed. Such a distance has been defined in the ECOROADS project by using a longitudinal friction coefficient of 0.40 (wet surface, high speed) and a 2-s reaction time. This gives the following stopping distances from various vehicle speeds (Table 2):

This minimum rule obviously applies to the opposite direction and also—maybe slightly modified due to reduced speed within the tunnel—at the exit of the tunnel and in the same direction (Figure 2 for each direction).

This area, actually its length, may only be extended after a common agreement of the expert team during a joint safety operations’ briefing meeting, who provided a sound justification for its modification. This need may emerge from other parameters, such as the speed mentioned above, road marking, signage, lighting, infrastructure design, and should then be considered.

Five joint safety operations performed during the ECOROADS project highlighted that such transition areas often presented the more critical road safety issues.

Since the common procedures adopted by the project have been validated through the success of the joint safety operations, the simplified scheme in Figure 3 can be successfully adopted by each infrastructure manager by using the checklist described in Section 4.

3. Conclusions

When managing the real traffic flows in the real infrastructure, there is a need for coordinated actions. This particularly applies to the transition areas where two different infrastructures (‘open roads’ and ‘tunnels’) meet, which leads to the need to develop a harmonised safe traffic management.

During the operations in the five test sites, there was a good level of involvement of infrastructure managers (of tunnels and open roads) and the core group as defined in the scheme of the previous Figure 1.

A multitask procedure was adopted to allow an experimental deployment of a multidisciplinary and multifunctional team of international experts.

ECOROADS has been funded by the HORIZON 2020 Programme [5]; the project collected 42 feedback forms from the expert group. Due to the rotation of the figures involved, all the members of the core groups were observers in at least one joint safety operation. There was widespread consensus on the following added value of the joint safety operations:

• Working in a mixed team (safety/tunnel experts), mixture of experiences from different countries

• Common/coordinated approach for open roads—transition area—tunnel in one project that guarantees a harmonised safety approach in the traffic management, respecting the different technical characteristics in each area

• Exchange of knowledge and best practices

• Opportunity to visit and see the tunnel from inside and see traffic and driver’s behaviour both inside and outside the tunnel (‘feel the traffic on my own’)

• Opportunity to examine the tunnel without traffic

• Close collaboration between road safety experts and tunnel safety experts regarding the common view of the transition area as a whole

• Mainly, the view of road safety experts on the part of the road in the tunnel with its specific characteristics can be very conducive to evaluate the total safety of the road in a closed environment (tunnel).

Acknowledgments

The study of the joint safety operations has been financed by the European Research and Innovation programme HORIZON 2020, through the project ECOROADS.