The critical factor here is that the task is repetitive, so it needs to be as simple and quick as possible, with bigger target areas. I think it's a good idea to keep with lots of buttons. One vehicle, one action - nice and simple.
Move the buttons a bit further apart to avoid accidentally hitting the wrong one and make them bigger so there's less room for error and try to make the button area look less congested and squeezed in.
I think the design of the buttons themselves adds to the noise. At the moment all your arrows are the same colour. I feel it would be better to have the arrows themselves coloured to better associate vehicle and direction. I'd also try and remove the grid like block pattern of the buttons, as the pattern is too distracting from the content. Perhaps move the buttons with the 'straight on' arrows forward a bit and make the buttons circular rather than square as there's too many straight edges at the moment.
Something like the following:
Matt's 'Lanes' idea is also a nice touch, tidying things up nicely:
Having gone through the multiple changes with the arrows, the round buttons and the lanes, then realigning the buttons horizontally at the top and vertically at the sides doesn't look so bad now - see below. I've also very slightly colourized the button backgrounds.
I agree with Vitaly that the button backgrounds still are a bit much - but I wouldn't remove them completely. I'd experiment with what looks good for your touch screen device but make them offer a clear target boundary area, whilst being minimal enough not to be invasive in their own right. Eg: