The international carriage of dangerous goods is regulated by the European Agreement Concerning the International Carriage on Dangerous Goods by Road (ADR). The 2009 Edition is applicable from 1 July 2009. EU Member States are required to apply the ADR provisions to national transport. ADr now includes new provisions, applicable from 1 January 2010, for the transport of dangerous goods through road tunnels.

The five categories  

Road tunnels have been assigned a range of five categories. Each tunnel will be assigned to a particular category following a risk assessment, including considering the availability and suitability of alternative routes and transport modes.  

The categories are:

A no restrictions

B restrictions for dangerous goods which may lead to a very large explosion

C restrictions for dangerous goods which may lead to a very large explosion or a large toxic release 

D restrictions for dangerous goods which may lead to a very large explosion, to a large to toxic release or to a large fire

E restrictions for all dangerous goods other than UN Nos. 2919, 3291, 3331, 3359 and 3373.

                                                                                                                                                                                                        ADR requirements covering tunnels are being introduced gradually throughout Europe. ADR contracting states are supposed to advise the United Nations Economic Commision for Europe (UN ECE), which provides the secretariat to ADR, of the tunnels that have restrictions (ie coded other than ''A''). Novadata will then publish them.

Read more details here.

All other tunnels are assigned to category A, with no restrictions.