I cannot see how you can apply your formula in any meaningful way in advance because two of the factors, mud & weather, can only be assessed on the day. This means that you can give a grade to a walk afterwards, but not in advance. Likewise with navigation, you can only tell how useful & accurate the route description was, after the event. That basically leaves distance & height which are the only constants and anybody reading a route description gets a good idea of what to expect of these anyway.

I think the Three Rings of Shap would hit top marks in most of my difficulty categories - foul weather, terrible surface and difficult navigation. Anyone who managed to complete it has my deepest respect!

The use of 'finish rate' to grade a walk's difficulty does pre-suppose the entrants are of the same mettle on all events. Conversely, if the entrants are made of tougher stuff for the tougher events, then the 'finish rate' would be perhaps more a measure of weather conditions.

Mentioned below, the 2012 Fellsman had a 30% 'finish rate' which was because it was stopped due to weather and 150 entrants retired by organisers edict. Fellsman 'finish rates' for the previous 10 years were a more respectable 68% (+/-10%).

The Dorsets have managed to achieve a far greater consistancy. On the Dorset Doddle there has been pretty much an 80% 'finish rate' for each of the last 3 years dispite quite different weather conditions.

Come and do Lake, Ridge and Wainwright held by our local group. Westmorland and North Lancs. 23 miles, 7500 foot of ascent with the nice Robinson and Dale Head ridgeline included as well as a little wonder up Maiden Moor and High Spy :)

Ridgeway results are out - 91.9% finish rate, and it was definitely not harder than the Poppyline.

Paul, the completion rate is certainly worth using as a rough measure of difficulty, but even then it's not absolutely foolproof - as well as how many people enter a walk, you'd also need to consider how those people were selected. Every 100 entrant is required to have completed a 50, ensuring that no-one can start it if they don't have at least some realistic prospect of finishing. The Poppyline required a 25 as a qualifier for the same reason. The Woldsman didn't explicitly require a qualifying event, but I don't expect anyone would have entered if they weren't well used to walking 30+ miles. I'm not familiar with the Fellsman, but I imagine it has some fairly strict entry criteria, since letting anyone attempt a course like that without sufficient experience would be extremely dangerous.

The contrast here is with certain non-LDWA events, which usually don't have any entry requirements and tend to attract less experienced, more casual walkers - I'm thinking in particular of the Stonehenge Stomp and Ridgeway here. Although official statistics haven't been released for the Ridgeway, from what I saw at the checkpoints the drop-out rate appeared to be higher than on the Poppyline and possibly the Woldsman - which certainly isn't because it was harder than either of those, but because there were more inexperienced entrants.

I can`t see how it is possible to rate the difficulty of any walk as it is far to subjective a matter and depends entirely on every individuals perception of what is difficult.

In my case I can go out one day on a walk/run get home and think that was easy I should have done more, then go out again a couple of days later cover the same ground and arrive home shattered, so If I was grading the walk which day would I choose for the grade?

As I say IMO grading walks is virtually impossible for the masses but an individual may be able to decide what is easy or hard for themselves.

I should have completed my research before the previous posting!

I believe that completion rates for, Poppy Line 50 was 93.75%. Remarkably, The Wye Forest 50 held on the same day as the Woldsman was also 88%.

All I can say is, you had a better chance of completing this year's Poppy Line, than the Fellsman !

Perhaps the best indication of an event’s difficulty is, how many entrants manage to complete it?

It it’s an easy stroll in good conditions then a high completion rate would be expected. If it’s demanding in difficult conditions then, surely fewer will manage to finish.

Looking at the percentage of completions should take into account some of the unquantifiable variables such, conditions underfoot together with the fitness / preparedness of the entrants. Factoring in the weather will always be difficult, because, if it changes during the event, backmarkers will experience different conditions from early finishers.

As a matter of interest, I believe that completions in 2012 included:
Woldsman 88% Games Hundred 78.5% Fellsman 30%
I’ll let you draw your own conclusions!

Thanks for the suggestions everyone. Darkness is certainly a factor, although this will very according to the individual - the fastest walkers on both the Poppyline and Woldsman would probably have finished in daylight, as one of the slowest I had 20+ miles in darkness on the former and 13 or so on the latter. Familiarity certainly helps with navigation - prior to this year the only challenge event I'd done was the Coventry Way, and although I now know that quite well, I still have to check the route description and/or map occasionally. I think remembering directions is probably a sort of innate ability, like remembering names or faces - I'm pretty sure I could walk the same route ten times and still not be able to do it without a map - but perhaps, like those, there may be techniques which can help you improve it. Following a waymarked path for all or most of an event also helps - whether or not you've done it before, navigation on the Ridgeway is practically non-existent as it just follows the same path for almost all the course, hence the very low rating for it.

John - you saw first hand how tough I found the Woldsman, so you shouldn't be too surprised at its high rating! As well as the weather and consequent mud, the other major area in which it scored over the Poppyline was the ascent - the Woldsman may not be the hilliest 50 around, but the Poppyline is almost certainly the flattest. Then again, if I followed Armorel's suggestion of factoring in checkpoints, the WP's difficulty rating would be boosted - although the quality of the checkpoints was excellent, there were 13 miles between CPs 2 and 3 and another 11 between 3 and 4, so you had to be self-sufficient for long stretches. The Winter Tanners would also gain difficulty points in that area - checkpoint facilities were basic (that isn't intended as a criticism of the organisers - the event was advertised as providing 'minimal support' and the entry fee correspondingly low).

Time limit - now there's a thing! How rigidly the limit is enforced varies - although no-one wants to hang around for hours waiting for one or two slowcoaches, most organisers will give a bit of leeway if you're not too far behind time. My usual pace for medium distance events is a bit under 3mph (on the 100 I was much slower); most challenge events have a limit which easily accommodates that, but there were a couple this year on which I anticipated that I'd be cutting it a bit fine: the Sevenoaks Circular (30 miles in 10 hours) and Oxon 40 (13). On the former I was late arriving at a checkpoint, the marshals shrugged it off and let me continue - come the appointed cut-off time I was a mile or so from the end and they agreed that it would be easier to let me finish than send someone out to find me. On the Oxon my companion and I were again late at a checkpoint, we were officially retired but decided to carry on independently - picked up the pace over the last 9 miles, arrived not long after the cut-off time and were reinstated. Thanks to the Thames Valley Group for being so accommodating on that one!

Fortunately I've yet to come across six foot high vegetation on a challenge event, but I did once when I was out walking by myself. Suffice it to say that I was rather slower than anticipated on that one...

A couple of omissions from your formula, perhaps.

You mention mud & rocky bits within your surface factor S. An additional consideration for factor S would be when paths are replaced by open country where vegetation can become a primary factor of walking difficulty. In the extreme, I remember folk up in North Scotland responding to my enquiries abuot how may miles a route was with calls of "We don't bother with the miles up here, laddie!"
When the route includes negotiating six-foot high heather on an ascent of some considerable height and steepness, you begin to appreciate where they are "coming from".

There is also the matter of speed or time limit which could preclude an easier, slower pace. The Centurian 100 miles in 24 hours is an obvious example. The Dorset Doddle (now an LDWA event but apparently when coined the name was seen as ironic) 12 hour limit regularly becomes a factor for walkers at the back of the field.

Fascinating and I'm wondering if there is something a bit more objective out in the world of walks statistics, eg doing a distance equivalent correction for ascent during a walk. Weather conditions, darkness, etc obviously subjective. Interesting to see our Woldsman high in ratings but purely down to the weather this year, I suggest, and navigation is related to familiarity with a route since lots don't change from one year to the next (for instance, how many seasoned Challenge walkers do you see refer to a map?)

Very interesting, Michael. I can think of various other factors (which you may well have considered) that might be taken into account, including the percentage of the walk done in darkness, the frequency and quality of checkpoints (on which the Games 100 must rate extremely well), and even the number of walkers, since if there are more entrants the chances are higher that the route in front of you will be neatly picked out by a line of nicely space walkers.

Having noticed considerable differences in difficulty level even between walks of the same length, in an idle moment I thought I'd try to come up with some way of quantifying these differences. I decided on five main factors which affect the difficulty of a walk, and awarded marks out of 10 for each:

Distance (D) - fairly simple, and the only one measured objectively: 1 point per 10 miles, rounded if necessary.

Hills (H) - takes into account the number, height and steepness.

Surface (S) - primarily concerned with the amount and depth of mud, but extra points can be scored for other features (uneven rocky bits etc.)

Navigational difficulty (N) - clearly it makes things trickier if you struggle to find your way!

Weather (W) - most points available for heavy rain, mist/fog and high winds, but excess heat or cold could also earn some.

Clearly not all of these factors are of equal importance: distance has a greater effect than any of the others, so I decided to calculate the overall difficulty as D(H + S + N +W). These were my results for the LDWA challenges I've done this year, as well as a couple of non-LDWA ones (the scores in each category are given in the order above):

Winter Tanners: 3(6 + 6 + 5 + 6) = 69

Stonehenge Stomp: 2(4 + 3 + 4 + 5) = 32

Winter Poppyline: 5(1 + 6 + 6 + 4) = 85

New Forest Marathon: 3(3 + 10 + 9 + 2) = 72

Sevenoaks Circular: 3(5 + 5 + 5 + 3) = 54

Coventry Way: 4(4 + 5 + 3 + 2) = 56

Woldsman: 5(9 + 9 + 7 + 8) = 165

Oxon 40: 4(5 + 4 + 4 + 4) = 68

Ridgeway: 4(2 + 3 + 1 + 2) = 32

Games 100: 7(7 + 9 + 5 + 9) = 210 (I've set D = 7 for this because I didn't finish, clearly if I had it would get an even higher score!)

The numerical results more or less confirm what I'd have said anyway: despite being marginally shorter, the Woldsman was far tougher than the Poppyline; the New Forest Marathon punched well above its distance; for a 40, the Ridgeway was ridiculously easy; and clearly the 100 was a level above anything else.

Feel free to agree/disagree with my impressions of the above events, offer ratings for others or suggest other criteria a difficulty rating ought to take into account. Does anyone think that such a rating system, or something similar (with the caveat that certain factors may differ considerably from one year to the next!), might be useful to give people some idea of what to expect from a particular event?