In Brunei Darussalam, an advanced amber warning system, known as the 'Prepare to Stop' (PTS) signals, are typically placed between 50 and 100 m from the stop-line along the junction's approach. The purpose is to reduce dilemma zone problems, instances of abrupt braking at red-light and reduce red-light running (RLR). This paper investigates the effectiveness of the PTS signals implemented on approaches of signalised junctions in Brunei Darussalam. Traffic data were collected on each approach for 2 hours per day over 10 working days using digital video recorders which were then analysed using Microsoft Excel, descriptive statistical cross-tabulation and regression tests in SPSS. The results comprised the rate of RLR at each of the studied approaches, average vehicles' travelling speed and the likelihood of vehicles decelerating and stopping at the onset of amber light in correspondence to the PTS signals. The outcomes showed that dilemma zone is extended by up to 275m along the approach and that most vehicles eventually stop at the stop line along the approaches with PTS signals installed. Most RLR cases observed for both junctions were not accidental but were deliberated by the drivers.