The design of travel lane configuration and lane width is crucial to traffic safety, especially in an urban mixed traffic environment where Powered-Two-Wheelers (PTWs) are prevalent and share the same roads with larger vehicles such as cars, buses, and trucks. However, there have been limited studies on the effects of the design of travel lane configuration and lane width on safety in such a mixed traffic environment. It's true the above-mentioned research question can be evaluated simply in terms of the number of crashes. However, doing so not only requires a few years of crash and traffic data, but limited insight can be gained in terms of how driver and rider behaviours are affected, and this has implications for further improvement in road safety. This study examines the changes in driving/riding behaviours and surrogate events before and after the adjustments of travel lane configuration and lane width by proposing a micro perspective approach as a complement to conventional studies. A before-and-after site-based investigation was conducted at two study sites which had opposite adjustments for travel lane configuration and lane widths: at one site the number of lanes was reduced, thereby widening the lane width in the outer lane on one road section, and at the second site the number of lanes was increased, thereby narrowing lane width in the outer lane on the other road section. The results showed that an increase in lane width resulted in a considerable increase in the number of speeding events as well as unsafe driving/riding behaviours and surrogate events related to lane splitting, lane sharing, and overtaking.