In California, lane splitting is not illegal so when traffic is especially busy you can ride between lanes. While the practice is permissible, you must still split lanes "in a safe and prudent manner." This means that if you split lanes when traffic is moving at 60 mph, or weave in and out of traffic, you can get ticketed accordingly. Be smart, and you'll avoid the eye of the law as well as stay safe; split lanes only when traffic is moving slowly, and don't go more than a few mph faster than traffic. We always split the two leftmost lanes, as they usually have the fewest cars changing between lanes. Always be extra vigilant when approaching an opening between cars in traffic, as that is obviously the most likely scenario for an unexpected lane change by an automobile into your path. Even if the far left lane is the carpool lane, it's the safest choice if you are going to split lanes, just be extra careful at the entrance and exit areas. Again, be smart about it and an officer will most likely leave you be.