Average speeds are really difficult to compare. My route has over 100 sets of lights and how I catch them will affect my average. In addition if you cycle into a headwind you'll get another speed even though you might be working your nuts off.
RLJing is not the only dangerous way of speeding up your average. Getting juiced up, dangerous undertaking or overtaking, the list goes on.
If you want to find out if your fast on a bike, try racing on a track.
That’s a better, safer and more fun way to find out whether you're whippet or a whale
or you could just enjoy your ride