Monday, 22 September 2014

Weaving all over the road ...


When I was a Sea Scout (1973-7 Hi to the 1st Scrabster troop!), Dick Message aka 'Skip' taught us how to tell if two vessels were on collision course. There are two equivalent methods:
  1. With a compass take a bearing on the other vessel, wait a minute and take another.
    If the bearing hasn't changed, you are on collision course. Change course. Repeat.
    Obviously, if both vessels change course and are still on a different collision course, slowing down can help, too !
  2. If there is land on the distant horizon, (or stars above it) see if the other vessel is moving fore or aft relative to the distant land or stars. If neither, ie the vessel is stationary with respect to a distant landscape, you are on collision course. Of course, it won't hold true for a nearby coastline, or if you watch for hours because the stars 'move' (relatively speaking).

    "All our eyes on the distant horizon" Join in, everybody !
What does that have to do with cyclists 'weaving all over the road', you ask ? Patience !

Hunting dragonflies, on the other hand, use precisely the opposite tactic, known as 'motion camouflage' ; they approach their prey along a curved line calculated to make themselves appear immobile against the background. At the last moment they 'loom' out of nowhere. I'm sure fighter-pilot aces do the same thing - 'diving out of the sun' is a special case.

But what about cyclists ...

There are interesting motorbiker discussions on Advanced Rider and SafeSpeed forum threads:
A 2006 briefing paper "How Close is Too Close" was written for MAG UK by Trevor Baird and Elaine Hardy in consultation with Duncan MacKillop, John Moss (ex Safety Officer Cheshire CC).

It dealt with ‘Sorry Mate I Didn’t See You’ accidents or SMIDSYs, which are also known in the literature as Right of Way Violation (ROWV) accidents.

The relevant concept here is "Don't ride in a straight line at a car".
Sounds obvious, but it is good advice at much longer range than you might expect - 20-100 metres.
  1. You would appear to be stationary, and therefore less visible.
  2. You would be on collision course
Navigators call this situation CBDR, for 'constant bearing decreasing range'.

Here's an instance of 'Looming' :


Now I'm not suggesting that everyone that weaves about is an expert in the theory of human vision and collision avoidance, but weaving may not be a bad thing. Even if the driver has seen you already, if you wobble a bit he might well give you a wider berth.




Other notable comments in 'How Close is Too Close ?' include
Motorcyclists are encouraged by government to wear bright colours and ‘whizzy’ patterns, when distinctive colouring and patterns were part of standard methods of concealment techniques used by the military.


Note that black is a great colour for visibility under certain circumstances. Against grass, sky, concrete or snow, for example. And fluorescent yellow will give poor visibility in a field of oil-seed rape.


Why cycling in high-vis may be not as safe as you think - [ theguardian.com ]
Want to cycle safely? Stop focusing on high vis! - [ London Cyclist ]

It has been unsuccessfully blamed in court
"The defence claimed that Mr Hilson’s black, red and white cycling gear made him difficult to spot."

The AA have another take on being seen:


Most common reasons why car drivers do not ‘see’ motorcycles approaching at a T Junction.
CamouflageFailure to pop-out from background
LoomingBelow threshold of detection
ThreatSeen but not identified as important
ExpectationRarity of encounter
UnderestimateSpeed less than actual
NegligenceDid not look
HiddenObstruction by foreground object
PhysiologyBad eyesight and restricted movement
Memory recallPop-out not retained
Chemical ImpairmentDrink or drugs
  • Causal Network
  • Shape
  • Shine
  • Sound
  • Shadow
  • Movement
  • Colour
  • Right of Way
  • Normality vs Inexperience
SMIDSY Avoidance
If the driver's head displays no motion then it is unlikely that your oncoming motorcycle will be displaying any either.  
 A gentle weave, so long as the driver is looking in your general direction, will be enough to change the relative angle.
SMIDSY Evasion  
The first part of an evasion strategy is having pre-planned somewhere to go (the softest available  option) when and if the SMIDSY occurs. Aim your head that way.
I really don't see 'Weave all over the road when approaching a junction' ever appearing in the Highway Code, but the DSA might take it on-board for their rider training schemes, or even individual riding instructors might use it ?

There's an interesting analysis 'Drivers’ perceptions of cyclists' by Basford and Reid (2002), investigating how and why motorists behave - they found it easier to overtake a wobbling cyclist than one that was correctly positioned in the centre of the lane.

There aren't many online videos of invisible cyclists - here's one :

Is it just an excuse for poor overtaking ? https://youtu.be/GctdFBvvnsE?t=23s


Some motorists just aren't very observant (or is the camouflage more effective than it looks ?):

Maybe it's a question of not being what drivers are looking for ?
You used to be able to buy reflective roadsign bags (UK 'Keep right' have sold out):
Broad Haven 'Keep Left' Rain Cover Only - [ howies ]



See also