I've had a similar idea -- how about adding red thermoplastic paint in the curb lane to remind drivers that they're passing a streetcar stop? I find that the stops with the most streetcar passing offenses are the ones that are not at an intersection (e.g., Dundas and College eastbound), and I suspect that many drivers are just unaware of their surroundings and don't realize that the streetcar is stopping to take on or let off passengers. Some bright paint on the road might be a good reminder. (Though honestly, the only solution is enforcement and ruthless ticketing.)