When you convert to Mph my achievement so far doesn't look so good.
country lanes (wide enough for 2 cars) 70%
Urban dual carrageway with lots of traffic lights (cars have 40mph limit - although its busy so they do 10mph avg) 30%
Over 15.7 miles I'm averaging 20.2mph on a MTB 44 x 11 gearing, with Continental GRand Prix 26 x 1 tyres.
My bike is light - 7,938g (17.50lbs)
Although I dont have aero bars - just flat MTB ones.
I've only been riding for 1 year, but covered between 6k and 7k miles
It a commute to work, but I compete with myself and motor vechicles. Its so busy, I get to work 5 mins fast on the bike than in a car
The calculation of analyticcycling is pretty realistic. I do not know if all people would agree with the wattage for novice/sports/elite level that I supposed, though.
I know, I can pedal around 250 watts for about 40 Minutes (SRM says so)and I think I´m not a novice (11.000 km/year). The 42 km/h on a flat course for 15 miles (~ 23 km) is realistic for me.
Also the elite speed seems to be realistic compared to some ITT´s I´ve seen (mostly they go faster).
Now it´s your decision when you´re a novice