Tunnel Safety


Risk Analysis

We conduct risk analysis studies for road tunnels, according to the requirements of European Directives on tunnel safety and transportation of dangerous goods.

The methodologies we use are in accordance with the guidelines of each member state where the tunnel is in operation.

The results of tunnel risk analysis concerning the passage of dangerous goods includes the tunnel categorization to one or more categories.

Tunnel categorization is based on the assumption that in tunnels there are three major dangers which may cause numerous victims or serious damage to tunnel structure:

Tunnel categories

Tunnel Category A
No restrictions for the transport of dangerous goods
Tunnel Category B
Restrictions for dangerous goods which may lead to a very large explosion
Tunnel Category C
Restrictions for dangerous goods which may lead to a very large explosion, a large explosion or to a large toxic release
Tunnel Category D
Restrictions for dangerous goods which may lead to a very large explosion, a large explosion, to a large toxic release or to a large fire
Tunnel Category E
Restrictions for all dangerous goods (except UN 2919, 3291, 3331, 3359, 3373 and limited quantities <8 tonnes total gross mass)

Very Large Explosions are categorized in detonations and deflagrations. Dangerous goods that can give rise in such explosions are explosives and gases under pressure transported in bulk. Flammable gases under pressure may give rise to hot BLEVEs, while non flammable gases under pressure may give rise to cold BLEVEs.

Large explosions can be the result of the release and ignition of the aforementioned dangerous goods carried in small quantities, such as in cylinders.

Large toxic releases may be the result of an accident with dangerous goods categorized in class 2.3 toxic gases transported in bulk, or class 6.1 toxic substances in liquid form evaporating very shortly due to the high volatility. Large toxic releases are very weird to deal with, because there is no obvious evidence to the personnel in the tunnel control room and therefore the emergency response plan is not being initiated on time.

Large fires can be the result of the release and ignition of dangerous goods categorized in class 3 flammable liquids and class 4 flammable solids. Large fires are characterised by the fact that the smoke layer stratification is disrupted in a very short time from the initiation of the fire and the back-layering effect is very intense.

Specific Hazard Investigation

We conduct Specific Hazard Investigations for potential tunnel accidents and incidents.

The studies include hazard identification, semi-quantitative analysis, CFD analysis of smoke propagation, tunnel user evacuation modelling, frequency estimation through Fault Tree Analysis and definition of fire development scenarios through Event Tree Analysis.

The goals of the studies are mainly the definition of minimum operation requirements, provisions to be included in emergency plans and proper mitigating measures.

A fundamental training document
  • Functional description of the tunnel
  • Identification of hazards
  • Choice of scenarios
  • Examination of scenarios

Expert Opinion
Our team of engineers

compile the necessary Expert Opinion

on tunnel safety in an integrated approach

Expert Opinion focus on compliance and operational issues, as well as international best practices. Initial, a gap analysis is being performed covering all requirements of the project specifications, including national legislative framework and national & international reference guidelines and standards.

Furthermore, different design tunnel elements are examined for optimised operation ensuring required level of safety.
Finally, examples from international experience are given as possible improvements of the present status.

Dangerous Goods Traffic Forecast

We prepare traffic forecast studies specifying and justifying the conditions expected for the transport of dangerous goods. A detailed analysis of the market is performed, while a benchmark analysis with statistics on transport of dangerous goods in European Union is made.

The model of liquid fuel distribution based on consumption data and location of storage facilities, is developed for the nearby geographical area of the tunnel.

Additionally, all potential industrial and agricultural activities producing or consuming dangerous goods are recorded and annual volumes are estimated.

Finally, on site counting of vehicles carrying dangerous goods for selected period of times is being performed, and the results are compared to the estimated ones, in order to have a sound and justified final forecast.

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