Modern Vespa

Motorcycles/scooters need to sit on/over the loop line in the ground, not pass over it into the box to trigger the light.

Seth

I'm going to do a Wiki on this at some point... 

There are different types of inductive loop sensors in use; some cities (like LA) may use different ones depending on who got the contract for that particular road project.

Here's a diagram here showing where to position a bike or scooter to trigger the sensor:

Source, with more details and explanation:
http://www.humantransport.org/bicycledriving/library/signals/green.htm

I just turned left on a red today as the light wouldn't change. I waited for a few revolutions, I'm pretty sure it's legal here - but probably up to a cop regardless.

Subd. 9.Affirmative defense relating to unchanging traffic-control signal. (a) A person operating a motorcycle who violates subdivision 4 by entering or crossing an intersection controlled by a traffic-control signal against a red light has an affirmative defense to that charge if the person establishes all of the following conditions:
(1) the motorcycle has been brought to a complete stop;

(2) the traffic-control signal continues to show a red light for an unreasonable time;

(3) the traffic-control signal is apparently malfunctioning or, if programmed or engineered to change to a green light only after detecting the approach of a motor vehicle, the signal has apparently failed to detect the arrival of the motorcycle; and

(4) no motor vehicle or person is approaching on the street or highway to be crossed or entered or is so far away from the intersection that it does not constitute an immediate hazard.

(b) The affirmative defense in this subdivision applies only to a violation for entering or crossing an intersection controlled by a traffic-control signal against a red light and does not provide a defense to any other civil or criminal action.