Dimming Led's

I have a sealed LED bar and was wondering if it would be possible to have it hooked up to parking lights and brake lights

a dim setting for parking and then a bright setting for brakes..

The LED has just a single pos/Neg

I would run parallel sources from brake / parking with diodes on each and then run a resistor on the parking. Would that be correct or am i assuming it is incorrect?

look into pwm. there are some with running/brake intput, which is what you would need.