Dagen H (September 3, 1967) marked the day when Sweden joined most of Western Europe and started driving on the right-hand side of the road.

Photograph by Winfield Parks, National Geographic
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    On September 3, 1967, Swedish drivers switched from driving on the left-hand side of the road to driving on the right-hand side of the road, a day known as Dagen H.
     
    Most nations have right-hand traffic (RHT) regulations, meaning the flow of traffic is on the right-hand side of the road. Left lanes are used for passing. The United Kingdom and many members of the Commonwealth of Nations (including India, Pakistan, and Australia) have left-hand traffic (LHT) regulations.
     
    Most nations with right-hand traffic regulations manufacture and import vehicles where the driver sits on the left-hand side. This is a safety feature, allowing the driver to see past vehicles in front of his or her own car. In nations with left-hand traffic regulations, most vehicles feature drivers on the right-hand side.
     
    Sweden’s drivers adjusted beautifully to Dagen H, which required massive changes in infrastructure as well as a huge public relations (PR) campaign. In fact, traffic accidents actually decreased after the switch.
  • Term Part of Speech Definition Encyclopedic Entry
    adjust Verb

    to change or modify something to fit with something else.

    campaign Noun

    activities designed to achieve a social, political, or military goal.

    Commonwealth of Nations Noun association of independent nations and dependent territories linked by historic and cultural ties, as parts of the former British Empire, and cooperating on matters of mutual concern, especially regarding economics and trade.
    construct Verb

    to build or erect.

    engineer Noun

    person who plans the building of things, such as structures (construction engineer) or substances (chemical engineer).

    import Verb

    to bring in a good or service from another area for trade.

    infrastructure Noun

    structures and facilities necessary for the functioning of a society, such as roads.

    manufacture Verb

    to make or produce a good, usually for sale.

    massive Adjective

    very large or heavy.

    nation Noun

    political unit made of people who share a common territory.

    Encyclopedic Entry: nation
    public relations (PR) Noun

    the art, science, and business of promoting an organization, person, or event.

    regulation Noun

    rule or law.

    traffic Noun

    movement of many things, often vehicles, in a specific area.

    vehicle Noun

    device used for transportation.