A bill to require all motorists in Colorado to use snow tires or chains during snowy months on Colorado’s major mountain highway has passed its toughest test in the state Legislature. The Senate Transportation Committee voted 5-0 for the bill to require snow tires or chains on noncommercial vehicles on Interstate 70, an attempt reduce accidents and mountain traffic. The measure has already passed the House. Senators amended the bill to say the requirement would be in effect when designated by state transportation officials, instead of November through May. Commercial vehicles like trailers are already under strict chain rules during winter and early spring. Republicans control the Transportation Committee and were skeptical of the measure, but ended up voting for it.