Possible Clues:

• Bituminous material for roofing, paths etc
• Might 35 across stop on the road?
• When parking, come to a stop, doing for road surface
• That's enough to make a serpent stop on the road
• Seems the serpent won't go on on the road
• Snake having rest on road surface
• Substance used in roofing and paving
• Might the snake stop on the road?
• Roofing material
• A tar containing a measure of acidity?