sentences:  The first steam tractor was produced by Charles Burrell & Sons in 1905 following changes in Parliamentary legislation which allowed one-man operation of traction engines on the public highway, engines however could weigh no more than five tons unladen and were limited to a top speed of .The prototype steam tractor was a single-cylinder design but in 1906 a compound-cylinder version was produced, and this proved to be by far the most popular version with customers.In 1908 the RAC organised a trial of competing makers' steam tractors to ascertain the best.