When Jerry asked whether we could find any story about why Percy Hawksworth filed a patent in 1913 for a safety device for the sides of motor vehicles, this is what I found online:

A lawsuit related to that patent arguing that there was nothing novel about it. Nothing new under the sun.

IN THE IIIGH COURT OF JUSTICE.-CHANCERY DIVISION. Before Mn, JUSTICE SARGANT. July lOth and 11th and 31st, 1919

Some quotes:

• A Patent was granted for Improvements in or relating to safety devices or life-
  guards for motor vehicles. One of the Claims was for A guard for a motor
  vehicle Consisting of a frame or the like carried along the side of the vehicle and
  crossing the path of the rear wheels at a slight inclination substantially as and
  for the purpose described.  At the trial of an action for infringement of
  the Patent, the only defences raised were want of novelty and of subjectmatter.
  It was proved that slatted guards of the same general construction as
  those described in the Specification had been in common use for many years between the front and back wheels of tramcars, and that the only difference in arrangement between those guards and the patented guards consisted in the fact that the tramcar guards, owing to the cars being run in either direction, were parallel to the sides of the cars, instead of being inclined to the sides. There was no constructional difficulty in giving the inclination to the guard. Guards similar to the patented guards had also been used for the front wheels of tramcars, and there was no constructional difficulty in adapting to the rear wheel of a motor omnibus the guards that had been used for the front wheels of tramcars. It was also proved that, in the prior Specification of P., guards for both the front and rear wheels of tramcars had been described, the inclination of the rear wheel guards being almost the same as that of the patented guards.
  Held, that in view of prior user on tramcars, of both side guards and front guards,
  and the publication of the Specification of P., there was no element of novelty or invention to support the Patent, and that it was invalid
• ” This invention has reference to safety devices or life-guards for motor vehicles. It is well known that many, if not most, of the worst accidents with motor buses or heavy motor vehicles are  caused by the rear wheels. Now according to this invention, which is intended more particularly for use on motor buses, a life-guard, catcher or fender is provided for each of the rear wheels, consisting of a frame carried at each side of the bus or vehicle in such a way that with only a slight inclination its rear end overlaps or extends to the outside of the rear wheels, and thus serves to push anyone who may have been knocked down, or otherwise comes against it, clear of the said rear wheels.
•  In this way if anyone should for instance be knocked down by the bonnet or front of the bus or other vehicle, and the driver has succeeded in clearing him with the front wheels, he will be pushed on one side by the advance of the inclined guard frame clear of the rear wheels, instead of being caught by the latter as frequently “happens.
• Similarly, if anyone should be accidentally thrown towards the bus from the side,
  as for instance by a side-slip from a bicycle, and thus come against the inclined
  fender, it will act in the same way and prevent him from going under the bus
  or vehicle and from being run over by the rear wheels.
• By the arrangement above described, a very simple efficient and reliable protection is provided against accidents from the rear wheels of motor vehicles and the device also acts as a side guard to close in and protect the side space between the front and
  rear wheels

See this previous post which includes an 1896 patent for side guards on tramcars/streetcars: History of Underride Research & Reports: 1896 to 2017