I think it would come down to what is likely to hit the stanchions cars, lorries and what speed will they be travelling at (site speed limit?) and how far are the stanchions away from the road. If vehicles are only travelling at 10mph and the stanchions are set back from the road then i would have thought it very unlikely for them to be hit by a vehicles or it would have to be deliberately. if they are right next to the road then some form o0f barrier may be required particularly if you have lorries that might misjudge a bend ore when reversing. I would say you need to do a risk assessment on each stanchion as to the level of protection it needs, what is the implication of a lorry hitting the stanchion and damaging the pipeline in terms of is there an emergency procedure to implement and the likely cost or repair and loss of business while the line is shut-down. With this cost estimate then this should give you some guidance on how much to spend on protecting the stanchions. Phil