Staggered work shifts, expanded bus routes and more than $1 billion in toll road improvements are part a plan to attack escalating traffic congestion in Plano.

Without swift action, Plano is headed for gridlock as a wave of companies moving into the Legacy and new Legacy West developments combine with growing companies that are already there.

New office buildings and corporate campuses, including some still under construction, will bring more than 15,000 employees to the area in the next 12 to…