Light trails

A blipless day today for various reasons. Had half an hour to spare at an appropriate time and needed a break so decided to attempt one item off my "must try" list - light trails. I have NEVER tried this before. I wasn't out for very long as it was -1 oc and I had left my gloves behind!!! I was freezing. Took 11 shots and this was the best. Tried different lengths of exposure with different results. Anyone know if there is a way to get a sharper result? (Although I am pleased with my first attempt!)