This paper describes several aspects of Czech research on the capacity of uncontrolled intersections, that were conducted with the aim of finding a suitable method of calculating capacity applicable to Czechoslovak standard on 73 6102. The method, developed in the 1970s, was based on Harder's principles and on observations of critical gaps. Two examples are presented of nomographs used for easy manual calculations. A table shows the values for critical gaps that are used in the standard. Ten years after the standard was prepared, new measurements of critical gaps showed reasonably good agreement with the standard values at intersections with more lanes on main roads. For several other cases, different values should be used in future versions of the standard; for example, smaller values of critical gap would be more suitable for intersections on single carriageways. Thorough analysis has shown that the TRRL methods are suitable for Czech conditions, so that the 1975 version of the TRRL roundabout capacity formula was used for the Czech standard. This standard emphasises the following two basic principles for correct roundabout design, allowing the proper weaving of traffic streams: (1) weaving with small weaving angle should be ensured by correct ratios of weaving width and length to entrance angle; (2) weaving with average vehicle speed should be ensured by proper entrance and central island radius.
Samenvatting