I did that the other day. I always keep a couple extra cheap blinky rear lights in my bag. I was getting off the train at about 6 am, pitch dark outside, and her comes a ninja coming up the steps. I looked a him, he looked at my bike and lights flashing on my leg (strips), helmet and rear of the bike, and looked startled. I reached in my pocket and said "here take this, you need something out there in the dark"