Car traffic is one of the most important sources of noise in urban areas, Its emissions may be reduced by improvements in engines, tires and road surfaces but this will not eliminate the problem completely in the near future. It is therefore important to evaluate this noise thoroughly when decisions between possible alternatives in projects that deal with city planning are discussed, An important step in this evaluation process is the calculation of noise maps for urban areas. The procedure is demonstrated without algorithms and formulas because these depend on national standards and other regulations. The calculation has to take into account screening and reflections by objects such as buildings and screens near sources or receivers and other topographic properties. Using noise maps and corresponding data files, possible alternatives can easily be ranked relative to the lowest noise impact for all practical situations, These calculations and rankings are demonstrated with a simple example. All illustrations, calculations and maps have been produced using the software program CADNAA which is a product of DataKustik GmbH.