In other places, parking may not be allowed at all (e.g. where there are double yellow lines (in Britain) or it may be allowed only for limited periods. Parking is not allowed on streets where building construction is in progress. Parking may not be allowed on streets that must be open to emergency traffic such as ambulances and fire trucks. Parking may not be allowed in the winter on certain streets that are marked "snow route". These routes must be clear of vehicles so snow plows can get through to do their job.