For this particular case, there is a (very) detailed account of the trial in the Maidstone Journal and Kentish Advertiser, 30 January 1896:
I.C. Heard ... was standing at the window of his cottage at Paddock Wood when he saw a horseless carriage go past with two persons in it. The carriage was proceeding at the rate of about eight miles an hour ... at once ...
Your assumption that there was a speed limit, measured im km/miles per hour, existed may not be true.
In a 1919 training book, based on the first national traffic laws of 1909, for policemen in Germany, the speed measurement was based on that of a horses gait.
Within a town:
no trotting in heavy traffic areas
For Automobiles it is stated that ...
In general, it is quite possible to gauge another's speed by following behind them in your own vehicle at a constant distance and take down the speed your own vehicle says it is traveling. This is how it was done before radar, and can still be done today. Where I live, last I saw it was being called the "pursuit" method.
Here's a sample ticket I ...
The question could be divided in two parts: First, when did they loose the title of King of The Sea to Aircraft Carrier, then when did the naval strategy change?
And of course, all of that should be considered in respect of each country's naval system.
The Germans aimed during WW1 to be challenger of the seas. They used battleships against UK's ...