I would go for a field every time, there are far too many obstructions on roads, lamposts being the prime concern, let alone overhead cables etc.. .Its different in the states, there being many empty "bare" roads to land in. .. .When you have a forced landing the the overall aim is to get onto the ground as safely as possible, preferably with as little injury to yourself as possible. If you can do that and leave a servicable or repairable aircraft then so much the better. I feel that a field provides a better opportunity for this aim.. .. .The only time I would advise using a road is at night... as you really cant see whats in a field at night... better the devil you know I guess.. .. .Thoughts appreciated