Our Cycling Grading System: How we grade and what the grades mean.
The grading method is available in an active content Microsoft Word document; this requires MS Word 2010, or later. The calculator document, called Cycalc, is available as a zipped file by clicking <here>. There is also a grade chart below, click <here> to jump to it.
The algorithm used in the calculator emerged from the analysis of many hundreds of cycle rides over a range of distance and difficulty.
The biggest problem is estimating the height climbed – all mapping systems and software has unavoidable error when establishing a value for height of accent and decent of a cycling route. And in Cyclac, using Garmin Basecamp, I found this error conforms closely to a Normal Distribution with a one standard deviation of ~200ft with distances from 10-miles to 45-miles. The most accurate height measure available is that collected by Google during its ‘Street-View’ image collection. Google’s camera vehicles were used to gather imagery and geographical data as they drove around the streets. These height data are all derived from on-board GPS, and are therefore the most reliable measure we have for the height of a particular location. Consequentially if a cycling route has been explored by Google Street-View (easy to prove in Google Maps) then the height value produced by Google will be very accurate.
Google Maps provides tools to plot routes and Google Earth can takes these routes and quickly provide a value for accent and decent. Distance cycled and accurate measures of accent are the two most important figures for grading a route. How these grades sit subjectively with the individual cyclist is down to the cyclist: an elite cyclist will have a completely different view to that of ‘ordinary folk’ (the likes of Julie and me). Therefore our cycling grades are for casual hobbyist cyclists, and try to express how much effort we feel for the cycle ride.
We grade the rides: ‘A’ (ambling), ‘B’ (bearing), ‘C’ (challenging), ‘D’ (demanding) and Ex (extreme). Each grade letter is further described by: mild, average and hard. And the extreme grade has four levels: 1, 2, 3 and 4 – the hardest cycle ride we have ever done is Ex4, and serves as a good upper limit (the ride was completely exhausting!).
How hard a bike ride is ‘on the day’ has other factors: was it windy, were you pushing hard to test yourself, etc. Therefore the grading system assumes no wind and an average 60Watts of power used during the bike ride (60Watts is around 250kCal of exercise per hour for the average person). The bike itself is also a factor: we assume gearing of ratios you get on mountain-bikes and hybrid-bikes – in other words, rarely do you have to be out of the saddle to push yourself uphill. Therefore the grading system assumes around 250kCal per hour, and should this value be exceeded then elevated grade values will apply.
Roads in the UK tend to have a reasonably consistent range of accent verses distance, covering a large range but averaging around 50ft per mile. At 50ft/mile cycling power of around 60Watts ‘feels’ right. However if the average height -v- distance becomes greater than approximately 80ft/mile, then 60Watts is not high enough a power to ride the road – elevated power is needed, and the grading system takes that into account.
Below is a chart for cycle rides between 10 and 44-miles with various accents and the grades are presented with an average cycling speed predicted. The colour coding depicts where various grades sit with respect to distance and accent. Amber and red are harder than 60Watts rides, where red are rides that not only have elevated power but also elevated grades. For example, 20miles with 2100ft of accent will most likely average 74Watts, and feel more tiring because of this. At even greater accent figures for the 20miles example the effort will be so great that additional grade levels are applied: at 2800ft of accent 86Watts will most likely be the average power and seven grades are therefore added making an otherwise hard-A route into a hard-D!
The green routes are easier (lighter the green the easier), the brown routes are harder routes (the darker the brown the harder) and the amber and red routes are, potentially, very hard.