That D-cell is going to be heavy on your helmet. $.02 is get a bright red strobe for the rear of your helmet like the new Superflash and one of those 3AAA cell Led headlamps that have a strobe function for the front. If you're in thick dense fog you're screwed strobe or not. The fact that the bus is BIG and yellow does a lot to ensure it's being seen and it's not going to be as damaged as you anyway.
This LED headlamp has a strobe function that's almost as bright as a xenon flash. It's very good.
http://www.petzl.com/en/outdoor/head...kka-2/tikka-xp
get a good charger and NiMh rechargeables. Not that great in very cold weather but I've been running these lights for five days/week with a couple of sets of batteries that are two years old.
http://www.tek-tite.com/src/product_info.php?id=3086
This xenon strobe is light.