I wonder just how many cars were being driven around in those days, and whether Harper's reactions were because he remembered the roads before any cars drove around at all, so were free of their noise and pollution.
Hundreds of motor vehicles in Britain c1900, and somewhere about 130 to 150 thousand by the outbreak of WW1, not evenly spread, so more in and around towns (including taxicabs and delivery vans in big cities), still barely any in the country.
My father used to regale us with stories of how he could still walk “straight down the middle of the road” the seven or eight miles along the A road into the next big town, seeing maybe one car or motor lorry in the process, in the late 1930s, and when I regularly cycled it in the 1970s it still wasn’t the complete nightmare of speeding traffic that it is now.
In 1950 about 1:20 households had a car, by the early 1970s 1:2, then it continued to rise, and the multi-car household became quite common, until saturation sometime c1995 I think. Parallel that with commercial motor traffic also shooting up, and the massive increase in speed of traffic, and one can probably say that although the Edwardians who remember the time befor motor cars felt the change keenly, the motor take-over of roads has really happened since the 1950s.