Are there any surprising legal ways to calm traffic in front of your house?

The road I'm living on has a posted limit of 50km/h but people regularly do 70+. It's very loud and feels unsafe to cross the street. The accepted form of traffic calming here (speeding tickets) isn't feasible because the police are apparently stretched thin already (go figure).

Some ideas I had:

• plant a tree as close as possible to the road
• put out a sandwich board with a daily motivational quote so people slow down to read it