<P> The use of appropriately designed segregated space on arterial or interurban routes appears to be associated with reductions in overall risk . In Ireland, the provision of hard shoulders on interurban routes in the 1970s reportedly resulted in a 50% decrease in accidents . It is reported that the Danes have also found that separate cycle tracks lead to a reduction in rural collisions . </P> <P> In some countries, the use of shoulders is optional for cyclists, who may choose not to use it for reasons such as: it being too narrow, inviting dangerously close passes at high speed by motorists; it having a road surface unsuitable for cycling or putting the path of the cyclist in direct conflict with the paths of other road users, such as those turning across the shoulder . Generally, the usable width of the road begins where one can ride without increased danger of falls, jolts or blowouts . A road may have a gravel shoulder, its edge may be covered with sand or trash and the pavement may be broken . </P> <P> Full - width hard shoulders are provided on most new, upgraded (from the 1980s onwards), and major national roads in the Republic of Ireland, especially on wide two - lane and dual - carriageway roads (the shoulders on most 2 + 1 roads are narrow however). They are defined within the official document the Rules of the Road as a part of the road that should normally only be used by cyclists and pedestrians . Their provision of on interurban routes in the 1970s reportedly resulted in a 50% decrease in accidents involving pedal cyclists . </P> <P> The hard shoulder is usually demarcated by road markings in the form of a single dashed yellow line with the addition of yellow cat's eyes . On motorways, and at critical points on other routes (e.g. between junctions or interchanges, or beneath overpasses) a solid yellow line is used, denoting additional restrictions on usage of the hard shoulder . At junctions and on - ramps and off - ramps, the yellow line peels away into the turn, with a dashed white line (with green cats' eyes) denoting a lane division following the main route (i.e. in most cases the road remains the same width, and a turn lane takes the place of the hard shoulder). </P>

When driving on a national road is it permitted to drive on the hard shoulder