Although the Hatfield tunnel has been doing some useful testing for just over eighteen months, the experience so far obtained is still limited as each new model brings its own special problems. It is perhaps still too early to give an account of the experience obtained, but because of the interest in this tunnel it was thought that an account, even incomplete, would be useful.

Almost every facet of experience so far obtained is related to some of the special design features of the tunnel and I propose to review some of the problems encountered during the design stages of the tunnel dealing with these design features, before reviewing the actual model testing experience.