It was a road research car for testing the skid resistance of road surfaces. So it would go around the country testing dfferent surfaces, mainly motorways. At the time the company had three tractions doing the same job, however ours was the only hydraulic one and its 5th wheel had a tap into the rear suspension to raise and lower the middle wheel. It also had a water pipe infront of the 5th wheel which was used to spray onto the tyre for wet tests. It had a big water tank on the roof for this purpose, a small seat in the rear where the person who operated the equipment would sit and the other side was the testing gear etc. In that first picture you can also make out the signs front and back warning of testing. The 5th wheel could be turned to increase friction.
So it wasnt a Citroen car it was used by the road research laboratories. Ive seen the vehicles they used after these and the ones after those, they eventually went onto trucks for the tests. It would appear that they now use trailers for these types of tests, which are still being used today.
Michelin also had similar cars, i know DS Safaris were used to test out the michelin tyres i believe. These cars had a similar set up to our traction with all the testing gear inside to measure when the wheels skids, what force etc and the 5th wheel.
You must have seen pictures of the massive DS Michelin developed to test out truck tyres? It would have the truck tyre in the middle like our traction had its 5th wheel but the DS itself had 10 wheels and two huge engines.
So these types of cars were made for tyre and road testing, ours was used for the roads. The equipment had been removed before we got the car, it had a big hole in the roof, no back seats and generally in a very bad condition.
74 RHD hydraulic 6Hs were built, ours was the only one which did this job. One of the other tractions which did the same job, but its not a hydraulic, is still around too, its a small boot version and was at the NEC classic car show in November. That too is now a conventional saloon car without its testing equipment.
The brakes are just drum brakes all round, non servo assisted.
Another interesting point about tractions in general is that they were one of the very first mass produced front wheel drive cars made. Some versions were also one of the earliest types of hatchbacks.
This is the company it used to belong to when it was new in 1955,
http://www.trl.co.uk/75/ - if you look at picture 19 that is the other traction which did the same job, the non-hydraulic, small boot version which is still around. Unfortunately they dont have any pictures of our car, other than the one in the first page of this thread. Our 6H was a bit later than that car, i think thats a 1953 or 54, even though it says its in 55, notice it doesnt have a roof mounted water tank.
Its now obviously back to how it was from new out of the slough factory, just a family saloon car. The lever to move the rear suspension is in the boot, it has high, medium and low, no intermediate like on the later Citroen models.
Chris.
There was NO rust on it ANYWHERE , I mean NONE !! It was so good it must be someones pride and joy now , I often wonder where it is !
Looking forward to driving the raid tan hill route again in a week, last year was excellent, hundreds of 2cvs, nice scenery and a nice final location. Though there might be snow this time. 
