The article deals with the determination of the effect of intersection control modes on vehicle delay times, or with the differences arising from the use of different control modes of traffic lights at low traffic volumes. It describes the methods used in the Czech Republic, and makes a brief comparison with neighbouring countries.In the second part of the article, vehicle delay times on traffic lights are determined using different methodologies and compared with reality. The HCM methodology (method of recording queue lengths in firmly fixed steps) was used and compared with the TP 235 Czech methodology for the calculation of delays and the method of direct measurement of each vehicle delay by a stopwatch. The results are in good agreement; considerable differences occur only in cases where more complex movements are involved (left turn in combination with giving priority to straight direction traffic). Furthermore, based on traffic surveys, vehicle delay times were determined and compared in the mode with
traffic lights on (i.e. TL) and after switching over to different TL control modes at low traffic volumes. Different traffic movements at the intersection were monitored at multiple locations for verification and comparison purposes. Based on the results, it is evident that in terms of delay times, any active TL mode used at low traffic volumes is rather counterproductive. Also, environmental impacts (CO2 emissions, CO, NOX) tend to grow in the active TL mode. The article
also presents the analysis of several model examples using micro analysis software and quantifies the above parameters. The last part brings the initial design of conditions under which TL switching off may be applied. Basic design and traffic engineering characteristics
are identified and their effect on the TL control mode is described.

traffic lights, HCM, intersection control mode, vehicle delay, environmental impacts