Two Las Vegas-style resort casinos proposed for Suffolk Downs on the Revere/East Boston line and 37 acres on the Mystic River in Everett raise new questions about age-old traffic troubles on prime commuter routes to Boston.

The two sites are about 5 miles apart, with Revere Beach Parkway, or Route 16, leading to both. The main entrance to Suffolk Downs is on Route 1A, one of the region’s most congested arteries.