A long run line (nylon covered cable made for that purpose) and a 2-3 foot
chain with a loop gives him the freedom of running up and down without
the constraint of being chained...but you need to be sure that it is
anchored up high enough so that he can't get tangles and the chain is
always above him (like when he is walked)...it's just a bad habit and habits
can be broken...is there anything he is afraid of or avoids? Put in in
front of your car for a while and see what his reaction is...there must be
something that attracts him to the front of the cars...he should not be
allowed to chase cars either...that can end up a problem also...good luck