Honestly it's as safe as you make it. Splitting traffic in California is normal and drivers are around it all day so they don't get pissed when riders split traffic. In states where it isn't legal the 4 wheelers may have a problem. I don't always split although it's a lot safer to split traffic at a red light than being the last person in line and have some cell phone soccer mom texting as she comes up behind me not observing stopped traffic. That happens way too much here California. I'm safer between cars even if it's a few cars up from the back of the line. I use other cars to protect me if that makes sense. On the freeway where I only go if I must, if traffic is stop and go I'm splitting traffic to get where I need to go safely. I understand why others don't like splitting and if I'm in no hurry I won't do it.