Frank Hills did not confine his business interests to the chemical industry. In the early 1840s he became known for the development of steam road vehicles. He should not be confused with John Hill, a slightly earlier inventor in this field. The best known promoter of steam road vehicles was Stratford based Walter Hancock and in 1839 Frank Hills travelled on a Hancock vehicle to Cambridge 'taking a lesson on steam carriage construction during the journey'. He later patented a gearing system, Fletcher, in 'Steam Locomotion on Common Roads' suggests that this gearing had originally been developed by Roberts of Manchester. The cars appear to have been made by the General Steam Carriage Co. Of East Greenwich. This was possibly made with Joshua Beale - who has been mentioned before in connection with naphtha lighting. Col. Francis Maceroni may also have been involved.
Some well-publicised trips were taken over particularly steep and difficult hills in the area but the venture seems to have been unsuccessful. Sixty years later Frank Hills' son, Arnold, was to take up road vehicle manufacture in the 'Thames' line of coaches and cars.