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Rickmansworth stands on three major modes of transport - road, water and railway. The more recent M25 motorway could be considered as a fourth mode of its own, but we'll consider it under 'roads'.
And we're not far from Heathrow and Luton airports, giving access to the fourth mode, aviation.
Starting with our roads, at the end of the eighteenth century:
By the 1790s there were two types of road – the turnpike, on which tolls were charged under the authority of an Act of Parliament and used to maintain the road; and the parish road, which served local people without charge, and was maintained by parish officers (the Surveyor of the Highways) with whatever resources he had, including a small rate paid by the parish ratepayers and the labour they were required to contribute. Roads of both sorts were used by both passenger (coaches) and freight traffic (carriers), and this article will concentrate on freight.
Long-distance freight traffic radiated, generally, from London, and since 1762 had in this area used the Sparrows Herne Turnpike. Traffic moving east-west had used the Reading and Hatfield Turnpike, enacted in 1768 and by-passing London by connecting the Great West Road and the Great North Road.  Traffic serving the rapidly-expanding industry of the north and midlands, however, was more likely to have used the Chester (Holyhead) road, which also had the strategic role of connecting London to Ireland, through St Albans than the Sparrows Herne through Watford – that does not seem to have operated on the same scale, and indeed one estimate has the St Albans route carrying 5 times the traffic of the Sparrows Herne.  Certainly the Sparrows Herne does not merit mention in the classic study of the turnpikes. 
But the vehicles on both were broadly the same – waggons weighing about a ton and a half drawn by up to eight heavy horses and carrying four, maybe five, tons of cargo; or two-wheeled carts drawn by a pair of horses and carrying about a ton, with a great range of variants in between. Most carrying was by the ‘common carriers’, firms of widely-ranging size operating in stages of about 25 or 30 miles at speeds of around two miles per hour.  They served towns along their route, with their operations based at inns and connecting with local carriers who completed the delivery to places nearby.
(to be continued)
References for this article:
 2 Geo. III c. 63, ‘An Act for repairing the road from the south end of Sparrows Herne on Bushey Heath, through Watford, Berkhamsted St. Peters, and Tring, by Pettiphers Elms to the turnpike road at Walton near Aylesbury’, for 21 years from July 1762.
 8 George III, cap. 50, ‘An Act for repairing, widening, turning, and altering, the Road leading from Reading, in the County of Berks, … Rickmansworth, Watford, and Saint Albans, to Hatfield, in the County of Hertford’, for 21 years from 1768.
 Dr Alan Rosevear, private correspondence (May 2018)
 W Albert, The Turnpike Road System in England 1663 – 1840 (Cambridge, 1972).
 Dorian Gerhold, Road Transport before the Railways (Cambridge, 1993), p.3.