Hastighet-flödessamband för mötesfria landsvägsutformningar

The Swedish Road Administration is planning to install median barriers on narrow two-lane rural roads with paved carriageway widths down to 9 m. Overtaking lanes will be added on the road sections where barriers are installed. The added overtaking lanes will make it possible to overtake on at least 15 per cent of the road length. The narrow roads with median barrier will therefore mostly get one lane per direction. The result will be a "sparse" 2+1-road as opposed to the conventional Swedish 2+1-design with a continuous overtaking lane that is alternating between the two driving directions. VTI has, by commission of the Swedish Road Administration, constructed speed-flow relationships for "sparse" 2+1-roads with different percentages of the road lengths including an overtaking lane. The speed-flow relationships are based on simulation using the Rural Traffic Simulator (RuTSim). Speed-flow relationships for a normal two-lane road and a conventional 2+1-road have also been constructed using the same method to allow comparison of the "sparse" 2+1-road designs with conventional designs. The length of the overtaking lanes has been assumed to be 850 m on the "sparse" road designs and 1 500 m on the conventional 2+1-design. Moreover, the road alignment has been assumed not to place any additional restrictions on the quality-of-service.