All Sweden's immediate neighbours drove on the right (including Norway and Finland, with which Sweden has land border). Most Swedes drove left-hand drive (LHD) vehicles. This led to many head-on collisions when passing on narrow two-lane highways, which were common in Sweden because of its low population density and traffic levels. Nonetheless, the change was widely unpopular, and had repeatedly been voted down over the previous forty years. In a 1955 referendum, 83 percent voted to keep driving on the left. In 1963, the Riksdag approved the change and established the Statens Högertrafikkommission (HTK) ("state right-hand traffic commission") to oversee it. It also began implementing a four-year education program, with the advice of psychologists.
The campaign included displaying the Dagen H logo on various commemorative items, including milk cartons, men's shorts and women's underwear. Swedish television held a contest for songs about the change; the winning entry was Håll dig till höger, Svensson ('Keep to the right, Svensson') by Rock-Boris.
As Dagen H neared, every intersection was equipped with an extra set of poles and traffic signals wrapped in black plastic. Workers roamed the streets early in the morning on Dagen H to remove the plastic. Similarly, a parallel set of lines were painted on the roads with white paint, then covered with black tape. Before Dagen H, Swedish roads had used yellow lines.
