Why do Britain, Japan, India and Australia drive on the left while much of the world drives on the right? The answer reaches back before cars—to horses, wagons, roads, laws, empires and choices that became part of everyday infrastructure.

In this Undercurrent History documentary, we trace how the two systems spread, why the map has surprising exceptions, and what it took for Sweden, Okinawa and Samoa to change sides.

CHAPTERS
00:00 A border that changes the road
01:35 Before cars: horses and passing
03:50 How Britain kept left
05:00 Wagons and the move right
07:55 Empire and left-side traffic
11:50 Exceptions to the simple map
14:00 Why switching is so difficult
15:25 Sweden's Dagen H
17:55 Okinawa and the change back
20:55 Cross-border engineering
22:00 A final exception
23:00 Why road habits endure

Sources and further reading:
UK Parliament — Parliamentary roads and the Highways Act of 1835:
https://www.parliament.uk/about/living-heritage/transformingsociety/transportcomms/roadsrail/overview/parliamentaryroad/
National Motor Museum — Early British road-side rules:
https://nationalmotormuseum.org.uk/help-centre/motoring-firsts/when-were-the-first-driving-tests-introduced/
Sveriges Radio — Sweden's 1967 Dagen H:
https://www.sverigesradio.se/artikel/6767655
Okinawa Prefectural Archives — The July 30, 1978 traffic change:
https://www.archives.pref.okinawa.jp/news/that_day/4780
U.S. Department of State historical background — Samoa's September 7, 2009 switch:
https://2009-2017.state.gov/outofdate/bgn/samoa/129701.htm

Visual reconstructions and thumbnail artwork are AI-generated illustrations. Narration and visual scenes may be AI-assisted; historical claims are presented for educational purposes.

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#UndercurrentHistory #HistoryDocumentary #LeftHandTraffic