For each level: the one change that earns your first star, a plan for two stars, and the full three-star solution, hidden until you ask for it. Every plan was played through the game's own traffic simulation.
One sensible upgrade usually does it. The first target sits just above what the town delivers if you change nothing.
Fix the right street, or two streets that work together. Which street matters more than how much you spend.
Usually only a few plans get here, and the most expensive plan is rarely one of them. Open the solution only when you're stuck.
Tap a street or junction to see what you can build there. Each level opens with a few more tools.
Each town's traffic is the same every time you play it. We ran every combination of upgrades you can afford on every level through the game's traffic rules and kept the scores. Road signs stay at their starting setup in these plans. Trying other signs is free and can add a few points.
Scores assume you buy right when the level opens. Pause first, buy, then let traffic flow. Where timing changes the result, the plan says so.