There is much information of building trailers and how to mount them to a standard bicycle. There are also many numufacturers of bicycle trailers. The law appears to be clear that pulling a trailer behind a bicycle is ok. It appears that red reflectors are required, by law, in california. And it is unclear if any lights are required, although many folks use the blinking red lights on the back of their trailers at night. Also, it may be the law that a reflector must be attach to each side of the trailer. Also, it may be required that the trailer have a red flag that flies at about 5-6 feet from the ground from the rear of the trailer, probably from the "passenger side"(car lingo) of the rear of the trailer.
What is not clear to me is what the rules are on pulling a trailer behind a "motorized bicycle", mopeds, or even scooters, electric or gas.
I have read some reports that a bicycle trailer, using same protocol can be applied for the bicycle trailer. I have read that what ever is required on the rear of the moped or scooter, including and/or a reflector, night "red" light, brake light, or turning signals, must be viewable from behind the trailer. If not, what ever reflectors and/or lights must be attached to the raar of the trailer or to the moped in such a way as to be viewable by traffic behind the bike and trailer.
If any of you have more info on the specific laws regarding this please send me the info and/or post that info in the comments.
Here is an interesting report I found about a guy in Oregon who purchased an electric scooter and mounted a trailer to it, and what his experience was like (with a picuter above).:
March 8, 2004
electric scooter with trailer My First Electric Vehicle, the scooter: I was driving a 10-year-old Subaru wagon that got 22 mpg, and I was hearing the alarms about the coming crisis in world oil supplies. My teenage son got his driving liscense, no longer wanted to ride the bus, and I thought three cars for three people was the height of financial insanity. Then I saw this extremely cute Chinese electric scooter for only $1200, and I couldn't resist. The construction is very cheap, the speedometer doesn't work any more, I've blown two battery chargers, but otherwise I have been impressed with the reliability and low cost of operation over almost 3,500 miles in one year. Insurance is not required in Oregon, but for $75 I thought liability coverage was a good idea.
I asked the salesman if I could pull a dog trailer, he said it would slow me down, and yes it would be possible. What he didn't explain is that I had to be very easy on the throttle, so I burnt up my first set of batteries in 5 months. Now I push the scooter by running beside it to get going from a dead stop, and jump on, which is just a little embarassing, to say the least. I get weak acceleration from the permanent-magnet, 700 watt motor on the rear hub. It has four 22-Amphour glass-mat batteries which gets me and my dog to work (5 miles), where I recharge for the trip home. I could make it home without the recharge, but the last mile would get pretty slow. I have to keep my speed below 15 mph, stay in the bike lanes or the bike-route streets, and on the streets without bike lanes it gets a bit scary. I ride in all kinds of weather, so I've learned to allow extra time to suit up in the required rain or cold weather gear. The comfort level and visibility at night, in the rain, in the winter is terrible. Thus, the motivation for a semi-enclosed, more powerful vehicle.
If I were to calculate the cost-to-benefit ratio of this project, I would never do it. To save money on my commute to work, I would continue riding the scooter and endure a few more winters before I retire. No, I am trying to be a small part of the change I want to see. The "humm-E-bird" is intended to be a statement of a possibility, an encouragement to the imagination of others.
Here are several links for scooter/moped trailer manufacterers: