Sunday, 28 October 2012

Vehicles per hour on the Cambridge commute

Way back in March 2011, the Police did one week automated speed surveys in Cottenham. Here are a few facts and figures with a focus for cycle commuters going to and from Cambridge. Cottenham is 7 miles north of central Cambridge.

The numbers are only for the peak hours Mon-Fri. Vehicles per hour are in one direction. Traffic levels drop off significantly outside of these hours. Averages are median of 5 days totals.

Histon Road 30mph, Southbound towards Cambridge:
08:00-08:59  762 vehicles per hour, one car every 4.7 seconds. 24% >35mph.
09:00-9:59   790 vehicles per hour, one car every 4.6 seconds. 15% >35mph.
The amount of traffic arriving at Twenty Pence Road on the northern edge of Cottenham is 74% and 76% of the Histon Road levels.

Histon Road 30mph, Northbound returning from Cambridge.
16:00-16:59  378 vehicles per hour, one car every 9.5 seconds. 24% >35mph.
17:00-17:59  566 vehicles per hour, one car every 6.4 seconds. 21% >35mph.
18:00-18:59  695 vehicles per hour, ne car every 5.2 seconds. 18% >35mph.
The amount of traffic exiting at Twenty Pence Road is 56%, 60% and 57% of the Histon Road levels.

Before 9am has always had an more edgy and rushed feel to it - my instincts are right. My instincts also tell me that 8:50am is a terrible time for speeding, worse than 8:30am and I have wondered if this is the gonna-be-late-for-work effect.

I have also noticed that traffic in the 4pm slot is running faster and I have suspected the white van effect. A quick scan of the raw data suggests that Category2 vehicles (>6m long) are only 10% of the traffic on Histon Road and do not speed more than other vehicles.  Exiting on Twenty Pence Road however, is a very different story, with a much larger proportion of vans and 10% higher speeds than category 1.

I've included the numbers comparisons for Twenty Pence Road as I sometimes wonder how much traffic is passing through the village as an alternative to using the parallel A10 trunk road.  The A10 typically queues from just south of Waterbeach to the A14 roundabout and the B1049 offers a parallel route. It is interesting to note the lower percentages of traffic passing in the reverse direction in the evening which gives a little weight to my theory.

The section of Histon Road between the mini roundabout and the beginning of the cyclepath is exactly 1km. This equates to 2-4 minutes of cycling (10-20mph range).  Assuming a rate of one car every 5 seconds, you are going to be overtaken by 24-48 cars on this stretch.  With typically a fifth of cars speeding at 36mph or more, you can begin to imagine how many unpleasant overtakes a cycle commuter must endure if they cycle on the road. It's not just the speeding cars, there are a lot of drivers simply wanting to overtake and may get frustrated by a slower cycle and oncoming traffic preventing an overtake if you ride away from the kerb. Kerb huggers will have many of these vehicles squeezing through.

You can halve the number of unpleasant overtakes by cycling at a lycra roadie speed of 20mph.  If you can't, that footpath must look like a safe haven, a necessity even.


I thought I might as well record how many cars pass me on this 1km stretch to see how it compares to the Police recordings.  I normally spend 2.5 minutes on Histon Road.


October half term school holiday week (i.e. very quiet)

Southbound Mon 08:50am. Just 6 passes in 2.5 minutes.
Southbound Tues 09:20am. 7 passes. Feels like a Ghost Town compared to normal.
Northbound Mon 18:30pm. An unbelievable 5, yes just 5.

November, during school term:
Southbound Wed 8:50am. 12 passes. (plus queue after I pulled onto path)
Southbound Thu 9:00am. 11 passes + 7 queued behind.
Southbound Fri 9:00am. 6 passes.
Southbound Mon 9:30am. 12 passes. (very little oncoming traffic, overtaking easy)
Southbound Wed 8:55am. 8 passes.
Southbound Thur 9:05am. 9 passes.

Northbound Wed 6:50pm. 6 passes (had to wait for traffic to clear)
Northbound Fri 6:00pm. 0 passes (very unusual!)
Northbound Wed 7:00pm. 4 passes.
Northbound Thurs 7:30pm. lost count, was distracted by overtakes at high speed.

I give up!  I lost count too many times when distracted by overtaking cars rushing to overtake in gaps that were too small. I'd end up concentrating on staying alive rather than being relaxed enough to count.


  • Southbound, when a normal busy week there is enough oncoming traffic to prevent cars overtaking if you ride out from the kerb. If you ride in the gutter the queuing cars will squeeze through.
  • Lack of overtaking opportunities because of oncoming traffic leads to frustrated drivers sitting on your tail right where you can't see them and where you feel most vulnerable.
  • Northbound, at the end of the cyclepath there is often a wave of traffic that has been released by the traffic lights in Histon.  Sometimes have to wait for the traffic to clear, sometimes it is clear then you get engulfed whilst on the road.

Wednesday, 24 October 2012

Dusk 'til Dawn 2012

The Dusk 'til Dawn (D2D) is a 12 hour overnight cross country mountain bike relay race held early October at Thetford Forest.

I took part in the D2D last year, and it was my first ever mountain bike race. It threw everything at us, rain, mud, cold, I got cramp for the first time ever, I took a tumble, I was ill the week after. But out of this hardship grew a challenge that presented itself not just at a personal level, but also at a team level which pushed me further than I would ever push myself and kept at bay that giving-up feeling. The event is completely devoid of bad attitude and from top to bottom of the leader board there is a really friendly atmosphere. It is such an inclusive event, challenging and fun at the same time with a whole heap of camaraderie.

Last year we put in some terrible lap times, but simply by not-giving-up and continuing as a team we pushed ourselves to just below average in the 3xMale category, 31st of 57. We were unbelievably chuffed with our first-time efforts and spotted that just one more lap would have boosted us to 16th place. We all knew we had room to improve and would have to come back in 2012 and give it another crack.  The Falloffalots would return.

2011 Lap times - Falloffalots
Lap 1 includes the pre-lap. My laps in bold.
(1) 01:12:33, (2) 01:15:40, (3) 01:08:16,
(4) 01:14:36, (5) 01:35:17, (6) 01:19:58,
(7) 01:42:49, (8) 02:20:29, (9) 01:35:30
Total time: 13:25:08
31st of 57


My normal training mostly consists of a 25 minute leg-it-to-work-and-back by bicycle in winter, and in summer I lengthen my commute in one direction to 45-60 minutes depending on the time I have available. I may also grab 1-2 hour ride every other weekend.

Some months before the D2D, I and one team mate started riding Thetford regularly together. Our aim was to get used to riding the terrain at a faster pace than we would on a social ride. Our abilities were not evenly matched which had the effect of making the slower rider sprint to keep up then have to go slow to recover, and the faster rider would have a sedate ride. We solved this by having a social ride to warm up and enjoy, testing out a few bomb holes, and then to finish an evenings ride with a full on blast round the full 10 mile Beater Trail (formerly the Red). At the same time we discovered Strava which added a fantastic virtual challenge. In the end I managed to achieve a 7th place overall on the Long Red segment.

As October approached, we got more practice in darker conditions and in the final two weeks before the D2D the car parks in the weekday evenings went from lonely to heaving.

Race Weekend

Logistics began by pitching our tents on the Friday night then returning home.  I'm glad we did, it was quite a chilly night. Kudos to those who were camping without heating on the night prior to the race. The third member of our team also arrived in the country, this time with two children in tow. In total there would be 3 racers and seven cheerleaders consisting of 2 wives, and 5 children.

I went first last year, and handed over the responsibility to our foreign team member. This year I was able to watch the start with my family. We all arrived and registered in good time, and from the arena I watched many riders go out to view the course in daylight. Same as last year I conserved energy by not bothering to view the course as I know my way round most of Thetford Forest. The race briefing came and went at 6pm then I watched as my team mates tried to get ready - finding black cycling clothes in a dark tent by torchlight - while bored children chased and screamed around them. Stresses and faff levels were high. Somehow I managed to maintain a zen like state and agreed to meet my wife and children at the start so I could prepare alone and think clearly.

At 7:30pm our lead out rider had escaped the family chaos and had already started queuing at the start line ready for the 8pm start.  When I showed, he was on the front row.  Last year we achieved similar lap times and considering we were completely average, I was starting to wonder if he had put in some serious training!

Get set, go !

7:55pm and I failed to find my family and bad reception meant I couldn't phone them, but did find my team mates family. At 8pm the gun went and all the riders chased the organiser's quad bike thing on the pre lap (used to spread the riders out before hitting single track). The line of riders went on for aaaaages.

Dusk 'til Dawn 2012 start

I found my family in the break and after about 10 minutes, the lead riders came back through the arena for their first full lap and boy they were flying. I wanted to spot our rider so I could judge how quickly he might return from his first full lap, but failed.  As the midfield came through, the audience decided that because they didn't know anyone, they might as well have a guess at names and shouted 'come on Dave!' to every rider.  My children loved the start, and my 6yr old boy was inspired - mission one accomplished - he wants to take part next year.  I said goodbye to my family who were returning home and very much looking forward to their warm beds and went to gather my things for my first lap.  I'll obviously need to work on the family if I am to get a pit crew.

Lap 2 - my first.

I came back to arena, had a chat with Wilburton Dick and my other team mate then rode around a little just to get my legs stretched.  Next I went into the corral waiting area in good time and went to find a place to park my bike.  It was heaving and there was nowhere to lean a bike on the fence.  Every time a rider went out another rider would arrive in the corral and manage to get their bike in the only free slot before I got there. After about 5 minutes I managed to park my bike.  I then waited with about 75 riders while bright lights arrived on the top of silhouette heads. After 15 minutes my team mate arrived. We exchanged band, and off I went, turning on my lights as I walked then jumped on the bike and onto the course for the first time.

Almost immediately I noticed I had an issue with my main light mounted on my head.  I've got cheapo Deal Extreme torches and I think one of my older batteries has a fault in the circuitry - giving it a bash made it bright again for about 30 seconds. I spent much of the first lap bashing myself on the head.

The initial part of the circuit was hard packed fire trail and was nice to warm up the legs, I was a little stiff and cold from standing around in the corral. I passed a few riders and felt pretty good. The course turned first to a straight grass track with a slightly slippery mud, and then into twistier single track, also with slippery mud. I saw a few fallers in this section.  It wasn't raining during the race but had the night before and the course was showing signs of wear, but praise-the-lord not wet!

Dusk 'til Dawn 2012 route

Somewhere around halfway into my lap, sweat had saturated the forehead foam in my helmet and was now constantly running into my eye.  This eventually caused me to lose a contact lense and I was having difficulty with depth perception, coupled with my light issues!  I locked onto the back wheel of other riders and used them as a guide, leap frogging ahead where possible but not being a hero.  I fell at low speed due to slipping on the side of a deep trench and landed on my ribs - ooof! They still hurt if poked three weeks later but not much during the race itself.

I recall Tom's pit being tricky, but managed to exit with only one dab at the top. I locked onto the wheel of a rider going a similar pace to me,  following for about 15 minutes and eventually got the confidence to pass after the Double Shocker. Almost immediately I fell again, slipping on a large tree root 45 degrees across the trail but immediately after a sharp corner, with my light I had no chance of seeing it. Hearing the music in the trees I knew the end of my one-eyed lap would be over soon, then through a tunnel of hanging colour array of glow sticks.  I came into the arena, whoohooped at the fabulously enthusiastic cow-bell ringers and handed over after 53m55s lap.

My gears were suffering after one lap so I rinsed my drive train under the dog tap, then returned to the tent. First changing into dry clothes, then having a cup of tea and a bagel with peanut butter and a Delia home wife-made energy bar, mmm nutty date apricot chocolate consensed milk yummy calories - no scientific gels or bar things for me. I chatted to our lead out rider before he went out again listening to his worsening cough, not good for the team. I got into my sleeping bag and just as I was dropping off it was time to get up again.  We knew that this years better weather would bring faster lap times, and less sleep time, but all teams were in the same boat. Our theory was that it would be harder to get up the leader board with less people giving up.

I got dressed reusing some of my clothes because I don't have four sets of cycling clothes, and nearing midnight, I went to the corral for my second lap.  I'd got there 15 minutes too early again and was starting to shiver after 10.  Most other riders had brought coats which they left with their arriving team mate.  Why had we not thought of that?!?  The corral was half as full this time, and many of the riders I would see again for each of my laps.

Lap 5 - my second.

I went out for my second lap, this time with working lights and contact lenses which put me in a jolly mood.  I spoke with other riders as I went round and had a great time. In the first 10-15 minutes I recognised and passed many of the riders I saw in the corral.  A pattern that repeated with every lap.  The course had also dried a little and the course was a lot more fun to ride as a result.  I had great fun through many sections, especially Tom's Pit this year, and the join of the Moto Trail and Double Shocker.  I'd picked up a couple of following riders and as I was shouting 'watch out for this root, I fell on the last ...'  thump.  'Ow, found it!' came the call from behind.  'OK?', 'Yes!' so I carried on.

Last year my lap times had deteriorated through the night. The mud and rain was tough and I didn't know at the time, but I was taking ibuprofen for back ache but had become allergic to it and it may have affected my ability.  This year I wanted to put in consistent lap times so did not push too hard.  I remember a rider coming past who was breathing so heavily on the fire road I heard his approach about 10 seconds before passing. He was unable to speak, and perhaps in hindsight I was taking it a bit too easy.  I remember the speed at which the Giant riders passed and it wasn't a huge amount faster, but they did get on the podium. I'd also found I was just a little faster than many riders but not fit enough to sprint past where small opportunities presented. I found myself overtaking mostly on fire roads. The faster riders just had a knack for overtaking in the singletrack without waiting. The lap was completed one and half minutes slower than the first in 55m12s, now close to 1am.

My break followed the same routine as before: dog-tap, tea, bagel and energy bar, bed.  I woke for my third lap feeling chilly.  My sleeping bag is a minimal summer one, and even with a silk liner and winter coat over the top it was not quite enough to overcome the chill. Next year I must get a giant motorhome and someone to service my bike.  This time I changed into a complete set of dry clothes and took my winter coat to the corral, so much warmer this time.

Lap 8 - my third.

My third lap felt like the hardest due to the low temperatures. In the open sections of the course it was really foggy with visibility below 50 yards and headlamps lighting water droplets in the air rather than the track ahead.  The fog made for some stunning views of riders in the distance, with a halo of light surrounding them fading to pitch black. Stunningly beautiful.  My third lap was 57m32s.

On my return I checked the leaderboard - we were averaging over 1 hour per lap as a team and we were at 27th of 45. Knowing we had one team member with a chesty cough, hopes of a top 16 place were dashed.  I still had a personal aim of keeping consistent lap times.

Dog tap, change, tea, bagel with peanut butter but this time getting sick of them as they were a little dry. I'd forgotten butter and ham which would have been a nice change.  I forced it down and had a home made energy bar.  After waking I took a few jelly babies.

Lap 11 - my fourth.

My fourth lap started sometime after 6am in the dark with dawn breaking about 20 minutes in.  The Air Cadets were stirring and in a great mood, me too shouting 'morning!' to everyone of them. They were fantasticly happy for people who camped out and stayed awake all night.

I knew each of my laps was slightly slower than the last and were getting dangerously close to one hour.  I pushed a bit harder on this lap. I'd also got the knack of overtaking on single track which was handy as the solo riders were starting to struggle now.  I shouted what encouragement I could for them, 10 hours in and still riding.  I flew through the Whoops on this lap, a series of deep roller-coaster dips that which could be cleared pretty quickly with some well timed pumps but lose rhythm or line and you would be at a near standstill.

The last third of my lap was in the early morning light and the forest never looked so good.  I worked hard to overtake one rider and she stuck with me for the rest of the lap which had the benefit of pacing us both.  We chatted on and off and I discovered she was in a female pair, Cookson Cycles / Velocake, the only entrant in their category. They completed one more lap than our male 3 and were on the podium later - well deserved.  We crossed the line in jubilant spirits, happy to complete our final laps and with our personal aims of keeping all our laps under one hour complete. I finished the lap in 56m05s - quicker than the last - and although tired at the finish line, felt that with a little rest I had at least another lap in me.

Our final rider went out and completed our 12th lap in a total time of 12h50m.  We had definitely improved this year but to the heady heights of 23rd place of 45, almost exactly average this year! Just one more lap would have boosted us to 13th place  ;-)

Lap times 2012 - Falloffalots
(01) 01:04:56  (02) 00:53:55  (03) 01:04:48
(04) 01:02:37  (05) 00:55:12  (06) 01:08:58
(07) 01:07:18  (08) 00:57:32  (09) 01:14:46
(10) 01:10:00  (11) 00:56:05  (12) 01:14:42
Total time: 12:50:49
23rd of 45.

I was pretty pleased with my improved performance this year.  My laps times were on a par with teams around 10th place in our category.  I have no idea how that might translate into a solo performance, guessing mid to lower table, but nowhere near the winning rider -  Paul Fielding - who put in 14 laps alone, 2 more than our three man team, covering 147 miles over the night. Doth's cap. What an effort.

What an event !  I enjoyed every minute.  I might have to a race in The Winter Series this year.

Thursday, 18 October 2012

Punctures between Cottenham and Histon

I recently punctured yet again on the Cottenham to Histon cyclepath.  A lot of other people have too and finger is being pointed at the stones scattered on the cyclepath opposite Cottenham Skips. It is theee worst location I have known for getting punctures (excluding an offroad location near Aldreth I've nicknamed Thorn Alley), and for some inexplicable reason it has been worse since the path was widened.

This short section of cyclepath has a bad track record for me.

Previously, I've tried my road bike on the Cottenham to Histon cyclepath but after puncturing twice in four journeys I decided it wasn't worth the risk. The stock Bontrager (Trek) 23mm tyres are fine on the road but no match for this cyclepath.

I normally commute on a touring bike, and for the summer I changed its tyres to 25mm Continental GP4000s to see how fast my tourer could go - surprisingly quick on the flat is the answer.  I had one slow puncture early on, I think after using them on the C2H cyclepath but otherwise fine all summer until my first night time commute, puncturing again on the C2H cyclepath. I paid the price walking the final 2km home in the rain.  I know I watch carefully for sharp stones in the light and dodge round them, but once dark you end up running over the sharp stones.

So, as much as I love the fast rolling 25's, I am hanging them up for winter and going back to my more heavy weight but more puncture resistant 32mm tyres for dark winter commutes.

My touring bike came with 32mm 700c Schwalbe Marathon (not plus) tyres and they have seen action for two winters, mostly on journeys between Cottenham and Cambridge, mixing roads and cyclepaths. This is what they look like now:

Splits after two and a half years of use.

This is the worst section of the tyre but all round there are splits of various sizes in the tyre.  Occasional  inspection reveals small sharp stones and glass embedded in the smaller splits which would cause lesser tyres to puncture. I recall how one of the larger splits happened: it was whilst cycling along White Fen Drove listening to music I became aware of an out-of-time beat. Removing my headphones I realised the sound was coming from my front wheel and with each revolution an arrowhead flint was being hammered into the tyre. My tyre was soft 10 minutes later in Stow-cum-Quy.

The Marathons have punctured on average every 1000 miles, but I discovered the root cause of most of them was a split that reached the inside of the tyre and would pinch the tube. I have since glued a patch inside the tyre.  Once my tyres are truly worn out, I might be tempted by the Plus version as a winter commute tyre despite the heavier weight.

If you don't like punctures, puncture resistant tyres can be worth the investment especially if you get a bike shop to repair your punctures.  One tyre that always gets consistently good reports is the Schwalbe Marathon Plus (£40+ per pair), with enthusiastic users quoting how many years they go without puncturing.  Recently I've also been told about years of puncture free life from Continental Contact tyres. (It is not one I heard of before but always like manufacturers to have competition or they get lazy and drop quality).

Friends at work also get saved by tyre sealants like Slime. It used to be dismissed by purists like myself but the use of sealants is spreading, as used in tubeless mountain bike tyre systems, and by pros on their winter training road bikes. I've not tried any sealants myself, worrying about potential mess and sealant lifetime I just prefer to fix a flat so long as it is not too often.

And finally, if you've ever had a fight with a bicycle tyre, you need to watch How to Fit a Schwalbe Marathon Plus Tyre. This video has saved my knuckles from losing blood countless times and I've not snapped a tyre level since watching it.

Monday, 15 October 2012

What Rural Commuting Lights ?

I thought this reply was worth a separate post to collect any comments and experiences from others.

Between the villages of Cottenham and Histon it is seriously dark and even with solar edge lighting you'll want for more lighting than the weak £20 set outputs.

It's a bit of a minefield buying lights and the technology moves fast and cost has been astronomical. Bear in mind that my product knowledge is very limited.

I have fair number of lights and would currently recommend those that contain LEDs based on on XPG-R5 technology for the general commuter - having a nice friendly spot and enough brightness. For road bikers who travel at speed or mountain bikers riding offroad at night, I would step up to XML-T6 which is even brighter and has a wider flood beam, but not too friendly for oncoming car drivers because of that flood effect.

I am using some cheap (unbranded) Chinese imports that use these technologies but wouldn't recommend that unless you are the type who owns a soldering iron.  I know someone who has Exposure branded lights and they are very good quality and also lots of money but will last you years. There are a lot of other good brands out there that I am not familiar with.

My friend has an Exposure Joystick which is based on XPG-R5 and it is bright enough for mountain biking round Thetford Forest at night. If you were a casual commuter you might be able to step down the range but research carefully. Confusingly the Joystick £145, Sirius £115, Spark £95 all run on the XPG-R5 technology, with different amount of Lumens (brightness). I just don't know which would would compare to my cheap Chinese torch.

The lights are expensive but what I can tell you is that over the last few years anyone I've met over the last few years who spent under £100 on branded lights has been disappointed with the light output.  Right now, £150 will definitely get you a branded light that meets commuter expectations, perhaps £100 will too but I just don't know.

I recommend looking for sites that compare light output from different lights. Torchy the Battery Boy's light database is a good place to start.  You might find your current light on there and beam shots from other lights so you can compare.

Now you know why a lot of people are taking (quality) risks with cheap Chinese imports. Told you its a minefield!  Over to the rest of the internet for opinions.

For more details on the lights I am running, see my previous post Night Riding Thetford Forest

Update: I fell across another set of beam shots linked from this front light buying guide. There's a nifty beam shot comparison feature with prices.