James - get an IR gun and measure the temperature at the water outlet elbow - do it both with the engine at what you consider to be "normal" operating temperature and also at the elevated temperature that you experience in heavy traffic - that way you will know if there is an issue that needs to be dealt with.
Dashboard temperature gauges are not calibrated precision instruments, and this is deliberate - it's done to prevent the average owner from panicking & making unnecessary calls to the dealer - the gauges are designed to sit at or near mid-point over a wide range of temperatures and only go to the red if the engine is on the point of overheating.
The fact that yours does not work this way is not cause for immediate concern, but, it could also be a sign of an underlying issue and should be followed up - especially the fact that the needle does move higher in heavy traffic - none of the Suzukis I've owned (and there have been several) do that - by verifying the temperatures you will know where you stand.