In the Margins of Error


When you’re riding in the margins of error, is a maverick homicide detective your only hope when it all goes wrong?

Wednesday March 30th 2016…

“So what we got Sergeant?”

“Open and shut case Lieutenant. Our guy was riding along the bike path, heading into town, hit a patch of mud and BAM! Wipe out!”

Pats pockets, “You got a match Sergeant?”

“Sorry sir, crime scene boys don’t allow it anymore.”

“Is that a fact?” Hand to forehead, scans scene, “Have they found that missing pedal yet?”

“Turns out our guy’s an amputee sir; one foot, one pedal.”

“You’re kidding me!” Turns to gurney and lifts sheet. “Well I’ll be… What else do we know about him?”

“Local oddball sir, rides everywhere, up until today we estimate he’s made this journey into Oxford about a thousand times.”

“Do we have a time of death yet Sergeant?” Lights cigar and checks glow, “And were there any other players involved?”

“11.55am this morning sir. We got a couple of witnesses who say he was alone; one second he was on the bike, moving slow, the next he was on the ground.”

“You know, I just don’t get it. It’s a sunny day, our guy’s done this a thousand times before, no one else around, and he’s got all this path to use but he’s riding in the mud right by the edge. Not only that, but it looks like he was turning in a way to pretty much guarantee he came down on the side he couldn’t put a foot down on.”

Gesticulates, “I mean what happened here? Did he have a heart attack or something?” Heads for car, “I’ll be downtown. Let me know what the autopsy says.”

Raises hand, turns and shouts over traffic noise, “And one other thing Sergeant, how the hell are you meant to cross the road around here?”

Still on the Streets

I’m not dead, despite not wearing the helmet I don’t possess. I was quizzed about that at both the Minor Injury Clinic on Wednesday and at the Hand and Plastic Injury Clinic on Thursday. I’d quite like to know what use is being made of the data. Am I right to bristle every time it comes up? Or does collecting it have a purpose that isn’t aimed at confirming someone’s bias? My daughter winces every time I’m asked, wondering how I’ll react this time, and I’d like to get to the bottom of it because in every other way the care I received in both clinics was beyond excellent.

I should be dead, but that would’ve been on the evening of Tuesday the week before, and therein lies the context to this incident, and the answers to Lieutenant Columbo’s questions. So lets back up a few miles to the site of my previous bad decision.

A Close Shave with the Reaper

Leaving Witney in the daylight, riding up Oxford Hill towards the A40, I’m passing the driveway where the previous week, coming back to Witney after dark, I’d joined the road to ride down the hill to the lights and carry on into town. I can see the brow of the hill clearly, although it continually changes as you move towards it. I recall the speed of the car lights cresting it as I headed off at an angle for the other side of the road, but now, I can’t fathom how our trajectories could not have connected.

I’m not a stranger to near-death experiences, but flashbacks aside, they’ve always been ‘in the moment’: hanging on in a broken body, fighting the temptation to slip into the welcoming warmth of its endorphins; off-balance, teetering on a kerb, every sinew straining against the slipstream sucking me into a lorry’s spinning wheel nuts; and the slow burn, the diagnosis that gives you more time than you really need to contemplate the void beyond the veil.

This was different; a chilling realisation of something I hadn’t been fully aware of. What had felt like another near miss, in retrospect, was a very near hit. From here on in I was preoccupied with increasing the margin for error I ride within.

Back at the Roundabout

Like every junction on the A40 bike path from Witney to Oxford, Eynsham roundabout has its problems. I’ve been honked at here more than once because I’m still crossing the road when a driver with more horsepower than anyone in an armchair needs is accelerating hard at me off the roundabout.

I was heading east aiming for the red circle. Normally, because of the mud on the path limiting my line of approach, when I get there I’m pointing at about 2 o’clock, which means scanning the arc between the blue lines for incoming missiles is bloody difficult; I’m struggling to look over my shoulder while at the same time trying to decide which exit drivers are aiming for.

It’s made more difficult because I’d rather not put my foot down. It’s not that I can’t start again – I’d never get going in the first place if that were the case – but under pressure, I don’t always get clipped in first time so I try to keep moving. And with a roundabout design like this there’s not much room for error because of the speed drivers can maintain, and as with all roundabouts, drivers are looking the other way as they enter at the danger posed to them. It’s only when they’re ‘on’ the roundabout that their attention is released to look at where they’re headed and the danger they pose to other cars. And other people.


Eynsham Roundabout

On this occasion, because I’m spooked and fixated on trying to increase the margin for error afforded me in this, frankly crap, cycling environment, my rational mind is set on following the red line to get me pointing to at least 4 o’clock when I get into the red circle, so I get a better view of incomings from the blue arc.

That means going against all my instincts and overriding my subconscious; my back-of-mind control centre with all the experience, the innate grasp of gravity, doing what’s necessary to maintain the maximum friction between my wheels and whatever surface we happen to be on, almost always keeping me upright, even on ice.

I didn’t make it to the red circle, and it didn’t end well.


The Fall

I was covering the brake to keep the hub motor disengaged, even though I was coasting at this point anyway (pedelec), but predictably, when I hit the mud on the left hand side of the path and tried to turn to the right ,the front wheel slid away and I went down hard. I must have put out my hand to break the fall while a bar-end punched me in the chest. Which hurt. A lot. I was worried I might have broken my sternum but it turns out that’s quite hard to do. I won’t be treating that as a challenge.

Apart from the bruise that’s come out on my chest, and another on my knee, I sustained a long spiral fracture to the 5th metacarpal in my left hand. It requires an operation under general anaesthetic to screw a plate to the bone so it’ll stay together as it mends. I’m back to typing one handed again.

I’m also left wondering – is it worth it? Persevering with using a bike as transport I mean. Does anyone give a shit about the practicalities of riding a bike in a world seemingly designed around the largest HGV and the crumple zone of the modern car?

Well. Somebody, somewhere, does.

Creating Time from Speed and Distance

Last year I went on another of David Hembrow’s study tours in Assen. I don’t recall precisely why we were at this particular roundabout now, probably because it’s just lovely, but we’d spent the day looking at various junctions and comparing them to their collision stats. What I do remember is having a little eureka moment.

I’ve ridden around many variations of the dutch roundabout now. The general idea, as I understood it, is the geometry is such that it defines the path of the motor traffic in a way that keeps speeds low while arranging the conflict points in a way so motor traffic and bikes are at right angles to each other for good visibility. Low speeds, good visibility, what’s not to like? Nothing, but I think there’s more to it than that. Or there can be as is demonstrated by this particular example.

The bike path around this one is bidirectional and cedes priority to motor traffic. What I loved about it is I could do laps around it in either direction without having to stop and put my foot down. It’s dependent on traffic volume I know, but there was motor traffic to interact with and this was the most  stressless experience I’ve ever had navigating a roundabout. And the reason? I had plenty of time.


Roundabout in Assen (mirror image)

There’s a trade-off in the distance from the road ring to the crossing points; too little and there’s not enough time for driver and cyclist to observe each other, too much and there’s too much time for the driver to accelerate towards the crossing. It also affects how far pedestrians have to go out of their way.

Keeping the road lane widths narrow at the crossing points is good, particularly for pedestrians, because it keeps the time to cross shorter, and it also means a longer island between the lanes for cyclists.

But I think what really makes this particular roundabout work for bikes is the relatively long paths at right angles to the crossing points. This extra distance gives the cyclist lots of time to observe the traffic which is in front of them AND creates time to adjust one’s speed to fit the observed gaps. It’s just hands down abs fab compared to the Eynsham roundabout.

Now I know a dutch traffic engineer would probably baulk at using this design for a volume of 25,000 vehicles per day, and I can imagine a british traffic engineer saying it wouldn’t have the capacity, but for the current configuration, with single carriageways all round, only flared within 20m of the roundabout to create dual lanes for the dual roundabout ring, I’d say the loss of stacking capacity would be minimal and traffic wanting to only turn right or left would just have to wait. By building from the outside in to reduce the Eynsham roundabout ring to a single lane would reduce speeds and create the extra space to lay out the bike paths in a cycle-friendly way. Lovely.

But that’s not going to happen, not least because the district and county councils are dead set on changing the configuration from single to dual carriageway in the long run, starting with bus lanes from Eynsham to Oxford in the short term until the cash is found to dual all the way to Witney.

A New Layout

The recent consultation document on the future of the A40 doesn’t say much more than there will be “Junction improvements to A40 at Eynsham and Cassington – part of Local Growth Fund Scheme”, but I’m guessing the detailed design must be starting about now.

I’ve seen surveyors with their lasers working at the Witney Road lights, and on the way back from the hospital on Thursday I saw a guy recording the flora and fauna along the highway boundaries. I believe the detailed design for the Eynsham roundabout is already drawn or in the process of being designed as I write. That’s a worry. I only remember seeing cross-sections of the links for the cycle path design from Eynsham to Oxford. There’s no indication what parameters and what requirements spec the contractors have been given to work to for the junctions, and my reading of the process during the Ducklington Lane improvements was, “Do the big stuff first so we can start modelling it, then we’ll fit the bike bits in the space that’s left.” [Sigh]

I’m all too aware that they’re just words, but given its commitment to cycling in Local Transport Plan 4, only an improvement on the existing situation should be acceptable to the county .

A Coping Strategy for the Existing Layout

Apart from clearing the paths of mud, what to do in the short-term? I always use the north-side bike path at Eynsham roundabout, purely out of habit I think, but it strikes me now that I have far fewer problems there when riding back from Oxford than when riding in. I think that might be because the arc I’m having to scan is narrower, and it’s starts at 90 degrees or less to my direction of travel, ie in front of me, as opposed to 90 degrees or more where I’m having to look over my shoulder at something behind me.

I need to try it, but I think crossing at the Witney Road lights on the way to Oxford rather than the Cassington lights could make negotiating this roundabout a lot easier. This strategy would mean I’m always cycling against the flow of traffic along this section, but the bike paths are not one-way here so that’s not a problem. However, if this were to apply more generally, does it follow that the way roundabouts with bike paths are designed in the UK is inherently flawed if cyclists feel they’re better off riding on the ‘wrong’ side of the road?

I’ve lined up a few ‘if’ statements there – what’s required is a way of assessing them quantitatively. Scratches chin.


Eynsham Roundabout

There’s one other caveat with this. A couple years ago a big (or bigger) tourist info sign was erected below the direction sign on the northern island meaning you’re unsighted until the very last moment when crossing it. How it ever got through a safety audit is beyond me. Perhaps there wasn’t one.


Collision Stats

I reported the incident to the police this morning via 101. Well, I say reported, I’ve got some reference numbers to quote. The guy I spoke to was sat in a Milton Keynes call centre but he started his career as a constable in Witney so he knew precisely where I was and where it happened. Nice chap.

He said if I did want to report it as an RTA I’d have to do it in person at Witney police station, although it’s closed at the weekends these days. However, there’s no legal obligation to do so with no motor vehicle involved, and it would make no difference to any claim I wanted to make. Which is fine, and I assume has something to do with bikes not being registered.

But what about injury statistics? I asked. Oh, I don’t know, he says. Not sure what the mechanism would be to record that without a motor vehicle involved.

Which in a country that’s in the grip of a cycling revolution [cough] seems a bit of an oversight. There have been many more than one bike-only incident along the A40 bike path, how will these ever get to inform, for example, the new design of the A40 junctions at Eynsham and Cassington? At the moment, I have no idea.

An Aide Memoire

In the hope of staying on top of the issues I’ve raised in this post, I’m parking this list here as a reminder for future reference. I wonder how far I’ll get with it…

  1. Request mud to be cleared from bike path.
  2. Can the sign added a couple years ago on the north arm island which unsights cyclists heading west be moved? Were the sightlines of cyclists considered before the sign was installed?
  3. Is there a design strategy or formulae in the Design Manual for Roads and Bridges which ensures bikes and pedestrians have sufficient crossing time on uncontrolled crossings around roundabouts? If not, do such things exist in NL, or are designers/engineers just being more considerate there?
  4. Request to see or discuss the spec and/or latest design drawings for the cycle path at the Eynsham roundabout.
  5. Are injuries from bike only incidents recorded and what is the process to ensure this particular incident is recorded so it can inform future design decisions? (Reference numbers from April 2nd: CNS01292, URN640).
  6. Follow up on the health service’s data collection of helmet wearing amongst cyclists in RTAs. Or is it Cs?
  7. How would one go about assessing roundabouts to determine whether it’s easier or less stressful to ride on the ‘wrong’ side of the road?


“Autopsy report’s in Lieutenant.”

“So what we got?”

“A lot of wear and tear, some broken bones, quite a few things missing but nothing critical. The doc says it’s highly unusual, but his body clock indicates he was living on borrowed time. Death’s been put on hold more than once and the doc reckons if our guy suddenly became aware of that, his mind would likely unravel as it realised he was living out of time.

“That said, official cause of death is Confirmation Bias.”

Eyebrows join raised arms.

“But sir, he fell from a bike without a helmet, chief says there’s simply no point in investigating it any further; case closed.”

Stubs out cigar, grabs coat and makes to leave, “Can you get me a bike Sergeant? I need to ride that route.”

“Who’s your suspect Lieutenant?”

Turns around with finger raised, “That Sergeant, is a very good question.”

3 thoughts on “In the Margins of Error

  1. davidhembrow

    Sorry to hear about your crash, and even more so for the self-serving reply, but the roundabout in Assen which you liked was the subject of one of my blog posts a couple of years ago because it really is a very good example. Read more about it here, including safety stats, a comparison with other less safe designs, videos etc.

    1. Kevin Hickman Post author

      Cheers David, and thanks for linking to your post with the video – helps get across a sense of how easy it is to use. Still no substitute for riding round it person though :o)

  2. Ian Dobbie

    One comment on the issue to travelling against the flow of traffic on the cycle path. On dark nights the cars lights are much more in your eyes massively reducing your view of hazards on the path. A couple do years ago on a dark and wet evening a car with ful beam headlights came over the top of the bridge over the railway and canal and I clipped the barrier end which cuts into the cycle path just west of the A34 flyover on the south side of the A40. Broke a rib and had an unpleasant few weeks recovering


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