Road surfaces influence transport networks and at the same time influence the quality of stormwater runoff. To assist with their management of road surfaces, the RTA instituted a monitoring program aimed at assessing the effectiveness of installed stormwater treatment devices in the SED4 catchment associated with the construction of a grade separated interchange at intersection of the Hume Highway, Roberts Road and Centenary Drive, South Strathfield. These devices include detention tanks, CDS GPT, and a sand filter. Instrumentationn was installed progressively from July 1977 at monitoring pits upstream and downstream of the treatment devices with all instruments operational from October 1997. Presented in this report are the results obtained from the monitoring program. From analysis of the data collected it was concluded that the devices installed were improving the quality of stormwater flowing from the road drainage system into the general catchment stormwater system.