An integrated GPS/GLONASS system was employed in this study to support the re-design of road networks and the adjustment of traffic control. The system was used to update road maps, and to determine the velocity and acceleration of a test vehicle. The vehicle ran along the traffic stream at designated times of a day, for specific time spans, to identify traffic conditions in urban areas of uncontrolled intersections such as roundabouts. Issues addressed included: transformation of GLONASS satellite coordinates from PZ-90 to WGS-84, the presence of the receiver clock error in the GLONASS double-differenced measurements, and the impact of the carrier wavelength variation on the ambiguity resolution. Two tests were carried out in an urban environment using the combined GPS/GLONASS system. The first test included updating a road map of a test area by an RTK approach. Results were checked by comparing them with an accurate map of the area, previously determined by conventional methods. The second test comprised determining position, velocity and acceleration of a moving vehicle representing the traffic flow for a selected area. Different solution schemes were investigated, including: RTK, DGPS, and post-processing of phase measurements. The impact of GLONASS augmentation and the quality of GPS satellites on solution feasibility and accuracy were also examined. Test results showed the benefits of adopting the integrated approach. These included: improving productivity and economics of map production, and improving availability, integrity, and accuracy of determining the velocity and acceleration, linked to positions on the road networks.