The following thoughts on comparing cycling between Scotland and the Netherlands are intended to be anecdotal, from my impressions of having been a cyclist in the Netherlands as a child and adult visitor; and as a commuter & recreational cyclist in Glasgow, Scotland for a year & ½. For more evidence based perspectives, please see blogs such as “A view from the cycle path” and “At War With The Motorist“.
The PCC: Blatant lies in headlines are just fine!
Given current events, I thought it might be interesting to dump details of a complaint I made to the PCC. It was a complaint about a Daily Mail article on a short report by EU MEP Dieter-Lebrecht Koch on road safety, which the Daily Mail ran a blatantly misleading headline on. When I complained to the PCC, I was amazed when they came back with a decision which you could paraphrase as “Blatant lies in headline are fine, as long as the article overall is more balanced & accurate“, despite the PCC Code of Practice requiring accuracy! Which goes to show how well self-regulation works!
The case against bicycle helmet advocacy: a quick guide
Bicycle helmets are tested with vertical drops from a maximum height of about 3m onto flat surfaces (BS/EN 1078:1997). In such testing, helmets definitely help. However, the scientific evidence on helmets & population wide injury rates is far from clear that helmets actually are beneficial.
While amongst cyclists who suffer injury, helmets of themselves do reduce head injuries significantly, they also increase neck and facial injuries, so that there appears to be negligible benefit overall (Accident Analysis & Prevention: … meta-analysis of bicycle helmet efficacy). Study of bicycle injury rates in Australia around the time of introduction of mandatory helmet laws suggests that, though there is a noticeable dip in injury rates around the introduction of the law itself (not necessarily attributable to the helmet itself in my opinion) that injury rates then started increasing again, to the point rates were nearly the same at the end of the study period as before the helmet law, and trending to surpass it! (My Blog: study-shows-australian-cyclist-helmet-law-leads-to-increasing-head-injury-rates). Helmet use also appears to induce risk-compensation behaviour in motor vehicle drivers – they make closer passes (Accident Analysis & Prevention: Drivers overtaking bicyclists…). No doubt the cyclists themselves also are subject to risk compensation. Thus, by wearing a helmet there may be an increased risk of getting into an accident.
There may be further population wide psychological effects caused by a culture of “Must be wearing a helmet to be safe!”. It is sending the message that cycling needs safety equipment, and hence must be dangerous, which surely will put off many – certainly where mandatory helmet use laws are introduced rates of cycling then significantly decrease. The reverse is of course true: the overall health benefits of cycling greatly outweigh the quite tiny risks – risks which are not greatly changed by helmet wearing, the studies appear to say. In other words, by advocating helmet use, one may be harming the rates of cycling by sending the wrong message on safety, and hence harming public health overall. Further, as cyclist safety on the roads correlates strongly with rates of cycling – more cyclists leads to more awareness & safer roads, and similarly fewer cyclists means less safe roads – this means a culture of helmet use may well lead to increased injury rates amongst cyclists (in addition to the general adverse public health effects of fewer people cycling). This would be very hard to categorically prove or disprove in causal terms, however the Australian experience certainly suggests a correlation, as I think would a comparison of the UK and Netherlands.
Finally, in the Netherlands, one of the safest places for cycling in the world, cyclists almost universally do not wear helmets, including very young cyclists. Thus, we can be quite certain that helmet usage is not a pre-requisite for safe cycling. Indeed, it is in places like the UK and USA, with some of the worst cycling safety in the developed world, where the focus on safety equipment for the cyclist seems to be greatest.
In short, the focus needs to be on those things around the cyclist (e.g. default legal liability to influence motorists’ behaviour, safer road infrastructure, etc) – not what is on cyclists. Focusing on cyclist safety equipment to me seems futile at best, and perhaps even detrimental to the cause of mass, safe cycling, if that’s a cause you believe worthwhile.
NB: Helmet use should always be a personal choice. The issue is complex, the trade-offs may differ greatly in different scenarios – helmets may be very beneficial in some settings, e.g. some kinds of racing. The choice should be your own. However, general advocacy of cycling helmets seems inappropriate and probably harmful, to me.
Is this rusty bollard safe for bicyclists?
Glasgow City Council have acted on my previous complaint to them, on the part about a bollard with a strange bit of jagged, rusty metal on top at the access to the quiet side road off the Broomielaw/A814, by having their cycling officer inspect it. The officer has found that it’s safe – sufficiently at least that no action will be taken it seems. I’ve taken photos of it, to see if anyone else might agree with me…
The new London Road cycle-path surface
It seems sending letters/emails to Glasgow City Council actually works. They instructed the contractor to fix the brand-new cycle-path on London Rd with the old, broken, road-surface. The end-result however is still a cycle-path with mostly an old & broken road-surface…
Distributed k-core algorithm
Earlier this year I gave at the talk at the March 4th, 2011 meeting of SCONE (Scottish Networking Event), on “Distributed k-shell graph decomposition”. The talk is on the k-core or k-shell of a graph, given in papers such as Seidman’s “Network Structure and Minimum Degree”, and it presents a new, efficient, distributed, algorithm for computing the maximal k-core membership of each node.
Reducing car/cyclist conflict: Dutch v Glasgow Style
Recently I sent a letter to GCC with some complaints about NCR75. To their credit, they appear to have acted on at least some of that letter (with thanks to Alison Thewliss for raising my letter with GCC LES) – they seem to clean the previously glass-strewn path a lot more often now, and they may have put up more signs to show which paths are meant to be shared-use.
However, regarding the Clydeport car-park entrance on the Broomielaw and how it interrupts and inconveniences the national cycle route that crosses its entrance with a dropped kerb, their response was:
At the Broomielaw, National Cycle Route 75 is located on the north side of the Casino, using a shared use pedestrian/ cycle track. Drivers exiting the Clydeport car park have poor sightlines, hence the kerbs nearest the wall on the cycle track have not been dropped, thus encouraging cyclists to stay away from this area, where they are harder to see.
Now, bear in mind this is an almost unused car-park – I’ve never seen a car going in or out there, even though I commute past there every morning and evening. The cycle-path there on the other hand is heavily used. Further, the kerb, though lower toward the outside, is still a raised kerb and an impediment to cycling! Never mind the road surface is also broken up to at least one side.
So the message is, when it comes down to the convenience of a large number of cyclists, versus that of a property holding company and its under-utilised, city centre car park for a couple of employees, well the cyclists can more or less go and get stuffed.
Update: Went past the Clydeport car-park later in the day today and it does seem full.
Entrance to the Clydeport car-park on the Broomielaw, with the National Cycle Route 75 crossing it. The cycle-path has a dropped kerb, very inconvenient for cyclists, particularly any carrying luggarge, and any on normal, non-offroad bikes. Note the cyclists having to stand up to negotiate the kerbs, even though they are out from entrance. Still looks like urban mountain-biking, sadly.
Another view of the car park entrance. Note that cars actually have plenty of visibility to this direction. It is only the wall on the other side that is impeding visibility. Note also the broken surface of the road, making the far kerb even harder to negotiate.
It is actually quite possible to engineer minor side-streets and entrances that must cross cycle-paths so that cyclists progress and safety is not compromised. They manage it all the time in the Netherlands. The line-of-sight issue could be better resolved by modifying the wall, and/or installing a lowish, progressive projection/kerb around the entrance wall to ensure cyclists move further out (indeed, this would be a good idea either way). Further, it should be Clydeports’ responsibility to ensure that its property does not impose undue risks on the passing public. At least, I would hope there is legislation and/or by-laws in place, to that effect.
So how do the dutch do it?
Dutch cycle-lane, with a minor-side-street junction. The junction is engineered to safely allow cyclists on the busier street the right of way over the quieter joining entrances. Note the conspicuous signage to remind drivers of the cycle lane, and note the concrete segregation barriers immediately before the junction, to prevent car drivers from turning in fast and early.
Note how the road is further engineered to slow down any cars before they cross the cycle lane, and so reduce conflicts. The cycle lane is raised up slightly with a smooth gradient, while the roads have a steeper kerb to negotiate, to force them to slow down and further help make them aware of the cycle lane.
Glasgow city cycling infrastructure, only for mountain bikers?
Glasgow City Council plan over the next few years to build new segregated cycling paths across the city. This is amazingly welcome news, of course. Work is already underway on a segregated path from Saltmarket, down London Rd towards the East End (to the under-construction velodrom perhaps?). Unfortunately, whether through lack of cash or lack of co-ordination and/or sheer institutional inexperience with building cycling infrastructure, the infrastructure that exists often comes with design and maintenance faults. At least, faults that would be immediately obvious to any regular cyclist. Unfortunately, the new segregated paths, though not yet finished, seem to suffer the same problem of some other such existing cycle paths in Glasgow: You need a mountain bike to use them!
Towergate Insurance and the Death Wish Cyclist
This is a comment I’ve sent to Towergate Insurance about their “Death Wish Cyclist” video, about which they recently put out a press release:
Hi,
I’m writing about your recent press release at:
http://www.prweb.com/releases/truck-insurance/accident-camera/prweb8592980.htm
In the press release you quote the truck firm, who appears to think his driver is completely innocent. This is a view which Towergate Insurance appears to endorse to some degree, as you have put the video on Youtube with the title “Death Wish Cyclist“. As a car driver and regular cyclist, I think it’s worth pointing out that the video shows the truck driver’s behaviour is far from perfect. Regardless of whatever blame may be attached to the cyclist, there are a number of problems with how the truck is being driven:
a) The Highway Code advises that cyclists should be left plenty of room when passed by motorists (rule 163 and 212). The road concerned is single-lane in each direction, and there is oncoming traffic, so the truck driver could not have changed lane. Yet they were still preparing to overtake, and even accelerated to 44mph as part of this. Had they passed the cylist, it would have been far too close and at too high a speed. The lorry driver was not intending to leave any margin of safety, needed in case the cyclist had to weave or move for some reason, e.g. from a mechanical problem or because of potholes. Motorists who close pass cyclists are driving irresponsibly, especially so when done with heavy goods vehicles which are almost to certain to kill cyclists if there is any contact.
b) The road is through Southampton Common and appears to have a 40mph speed limit. Yet the video shows the driver reaching 44mph as they prepare to overtake. They appear to be committing a quite obvious offence with their aborted overtake, presuming the data from your system is accurate.
c) There is a side junction ahead, which presumably is easily visible given that the cyclist was manoeuvring to take it. The Highway Code rule 167 states “DO NOT overtake where you might come into conflict with other road users. For example: * approaching or at a road junction on either side of the road“. The Highway Code says this precisely because road users are likely to be manoeuvring to leave or enter the road ahead – as the cyclist is.
d) The Highway Code also states that motorists should take extra care around vulnerable road users, such as motorcyclists, cyclists. Further, though it’s impossible to be certain because the camera lens is extremely wide-angle and doesn’t show enough detail, the cyclist looks like they perhaps may be young – a teenager. The highway code specifically advises motorists to be particularly careful around young and inexperienced road users (rule 204).
Road safety requires that we not only avoid making mistakes, but also that we take care to allow for the inevitability that mistakes will sometimes be made by others. On this basis alone, the driving shown by the truck driver was less than perfect. Further, the driving shown appears to directly contravene a number of rules given in the Highway Code, with which all drivers should be familiar. Finally, contingent on the accuracy of your system, the driver may even have been speeding.
All together, it’s very hard to see how this driver is “blameless” for the narrowly averted accident shown in this incident. Without intending to absolve the cyclist in any way of blame for their part, I think it’s important that anyone watching that video should also realise that the driving shown falls far below what is expected of motorists.
Cerf and Kahn on why you want to keep IP fragmentation
In “A Protocol for Packet Network Intercommunication“, Vint Cerf and Bob Kahn
explain the basic, core design decisions in TCP/IP, which they created. They describe the end-to-end principle. What fascinates me most though is their explanation of why they incorporated fragmentation into IP:
We believe the long range growth and development of internetwork communication would be seriously inhibited by specifying how much larger than the minimum a packet size can be, for the following reasons.
- If a maximum permitted packet size is specified then it becomes impossible to completely isolate the internal packet size parameters of one network from the internal packet size parameters of all other networks.
- It would be very difficult to increase the maximum permitted packet size in response to new technology (e.g. large memory systems, higher data rate communication facilities, etc.) since this would require the agreement and then implementation by all participating networks.
- Associative addressing and packet encryption may require the size of a particular packet to expand during transit for incorporation of new information.
Fragmentation generally is undesirable if it can be avoided, as it has a performance cost. The fragmenting router may do so on a slow-path, for example; and re-assembly at the end-host may introduce delay. As a consequence, end hosts have for a long while generally performed path-MTU-discovery (PMTUD) to discover the right overall MTU to a destination, thus allowing them to generate IP packets of just the right size (if the upper-level protocol doesn’t support some kind of segmentation, like TCP, this may still require it to generate IP fragments) and so set the “Don’t Fragment” bit on all packets and generally avoid intermediary fragmentation. Unfortunately however PMTUD relies on ICMP messages which are sent out-of-band, and unfortunately as the internet became bigger, more and more less-than-clueful people became involved in the design and administration of the equipment needed to route IP packets. Routers started to either ignore over-size packets and (even more commonly) firewalls started to stupidly filter out nearly all ICMP – including the important “Destination Unreachable: Fragmentation Needed” ICMP message needed for PMTUD. As a consequence, end-host path-MTU discovery can be fragile. When it fails to work, the end-result is a “Path MTU blackhole”: packets get dropped for being too big at a router while the ICMP messages sent back to the host get dropped (usually elsewhere), meaning it never learns to drop its packet sizes. Where with IP fragmentation communication may be slow, but with PMTU blackholing it becomes impossible.
As a consequence of this, some upper-level applications protocols actually implement their own blackhole detection, on top of any lower-layer PMTU/segmentation support. An example being EDNS0, which specifies that EDNS0 implementations must take path-MTU into account (above the transport layer!).
So now the internet is crippled by an effective 1500 MTU. Though our equipment generally is capable of sending much larger datagrams, we have collectively failed to heed Cerf & Kahn’s wise words. The internet can not use the handy tool of encapsulation to encrypt packets, or to reroute them to mobile users. Possibly the worst aspect is that IPv6 completely removed fragmentation support. While there’s a good argument that end-end level packet resizing may be more ideal than intermediary fragmentation, as IPv6 still relies on out-of-band signalling of over-size packets, without addressing that mechanism’s fragility problem, it likely means IPv6 has cast the MTU-mess into stone for the next generation of inter-networking.
Updated: Some clarifications. Added consequence of how PMTU breaks due to ICMP filtering. Added how ULPs now have to work around these transport layer failings. Added why fragmentation was removed from IPv6, and word-smithed the conclusion a bit.
