Overtaking

[Wossname]

Stimulated by SLG’s near miss thread….

I’ve been wondering for some time how much space AND time you ‘actually’ need for a safe OT, and if there is a way to calculate it. I’m not really a sums person but I’m sure there’s somebody on here who is, so…

A few givens to start us off to make it easier:
Bike doing 60, ordinary A-road;
Target vehicle (eg car 5m long) doing 50 and/or 55 so speed differential is 10/5 mph;
Take-off point 2 secs behind target;
Landing point 2 secs ahead of target.

Overall a very common scenario.

There you go. It should then be easy to adjust for different speeds/differentials/ longer vehicle eg HGV etc. So please show your workings, not just the answer!

Gives you something to do while the sprouts are cooking.

[Horse]

I've heard of (it was linked on another forum, ages ago) an Excel calculator.

Something it showed was the difference between the two types* of overtake, in that one needed earlier commitment so increased time exposed to danger.**

* Two types***:
- Follow, at same speed, then move out
- Catch up with slower vehicle, maintain thatconstant speed during overtaking

** Don't bother challenging me on this, not my spreadsheet and I never used it.

*** I call these 'Z'**** and 'S' overtakes, because of the (very approximate) path taken

**** I think this is sometimes called a 'box' overtake.

** (Part 2) Because the Z means you're keeping options open. S means you have to commit from further back.

[crust]

I would have thought that it will vary by bike and rider.

Bike - Acceleration - Available power and whereabouts are you in the powerband. A GSXR1000 in mid powerband will do the job a lot quicker than a Royal Enfield, a two stroke off the powerband will a few downchanges to get going quickly.

An experienced rider (or nutter) will be able to judge the acceleration and/or correct gear better than a novice/hesitant rider.

How risk averse is our subject?

[Wossname]

I intentionally put in some fixed speeds in this because I didn’t want to simply get the “I’ve got an S1000RR and I’ll be part in a flash” replies. It’s assuming sticking to speed limits, to give a sort of baseline distance/time. The only effect type /size of bike will make is if you’re talking about a 125 or similar, so again, assume we’re on a 600 upwards which most of us are.

[Horse]

An experienced rider (or nutter) will be able to judge the acceleration and/or correct gear better than a novice/hesitant rider.

How risk averse is our subject?

How old? Eyesight deteriorates with age, will affect judgement of distance.
How tired? Tiredness is an impairment.

[Cousin Jack]

I intentionally disregard speed limits during overtakes. I may resume the correct limit afterwards, but if I am passing a vehicle doing 50mph in a 60 limit I am NOT going to be watching my speedo and throttling back mid overtake. And the bike makes a huge difference, overtake that on the VFR would be easy now require a bit more planning on the CB500. The real advantage of the faster bike was not so much the maximum power, but that you had enough power to start well down the rev range, and could complete without even considering changing up.

[Dickyboy]

I'm not sure why you'd want to ever bother calculating that, as in real life situations there are so many more variables to consider, knowing that the overtake I'm about to go for will theoretically take me 3s or 10s at nsl is neither here nor there.

[Count Steer]

I intentionally disregard speed limits during overtakes. I may resume the correct limit afterwards, but if I am passing a vehicle doing 50mph in a 60 limit I am NOT going to be watching my speedo and throttling back mid overtake. And the bike makes a huge difference, overtake that on the VFR would be easy now require a bit more planning on the CB500. The real advantage of the faster bike was not so much the maximum power, but that you had enough power to start well down the rev range, and could complete without even considering changing up.

Yeah. I was told, if you're going to do it, get it done. Minimise the time you're exposed/on the 'wrong' side of the road etc.

[Skub]

And...when you wheelie,make sure it's a standup so you can still see.

Safety first.

[Horse]

I intentionally disregard speed limits during overtakes. I may resume the correct limit afterwards, but if I am passing a vehicle doing 50mph in a 60 limit I am NOT going to be watching my speedo and throttling back mid overtake. And the bike makes a huge difference, overtake that on the VFR would be easy now require a bit more planning on the CB500. The real advantage of the faster bike was not so much the maximum power, but that you had enough power to start well down the rev range, and could complete without even considering changing up.

Yeah. I was told, if you're going to do it, get it done. Minimise the time you're exposed/on the 'wrong' side of the road etc.

'ish'

That advice is often taken as meaning 'go as fast as you can't.

But potentially that means that if anything goes wrong you'll have a higher speed differential from the vehicle you're overtaking and travel further before taking any action.

Worst case is that it encourages using smaller gaps with reduced margins.

And worth noting that 'overtaking' is high risk, and one of the three 'gotchas'. RoSPA noted:

" In Clarke et al’s (2004) study, in 16.5% of accidents where the rider was considered partly or fully to blame, the rider was overtaking another vehicle."

[Rockburner]

I intentionally disregard speed limits during overtakes. I may resume the correct limit afterwards, but if I am passing a vehicle doing 50mph in a 60 limit I am NOT going to be watching my speedo and throttling back mid overtake. And the bike makes a huge difference, overtake that on the VFR would be easy now require a bit more planning on the CB500. The real advantage of the faster bike was not so much the maximum power, but that you had enough power to start well down the rev range, and could complete without even considering changing up.

Yeah. I was told, if you're going to do it, get it done. Minimise the time you're exposed/on the 'wrong' side of the road etc.

'ish'

That advice is often taken as meaning 'go as fast as you can't.

But potentially that means that if anything goes wrong you'll have a higher speed differential from the vehicle you're overtaking and travel further before taking any action.

Worst case is that it encourages using smaller gaps with reduced margins.

And worth noting that 'overtaking' is high risk, and one of the three 'gotchas'. RoSPA noted:

" In Clarke et al’s (2004) study, in 16.5% of accidents where the rider was considered partly or fully to blame, the rider was overtaking another vehicle."

Has to be said - these days I tend only to go for overtakes if I can see an actual gain to be had (especially if I know the road well enough).

EG, why overtake the 3rd of a line of 3 cars if the next 10 miles is so twisty you'll be stuck between 2 and 3 for the forseeable: there's no benefit.

[Count Steer]

I intentionally disregard speed limits during overtakes. I may resume the correct limit afterwards, but if I am passing a vehicle doing 50mph in a 60 limit I am NOT going to be watching my speedo and throttling back mid overtake. And the bike makes a huge difference, overtake that on the VFR would be easy now require a bit more planning on the CB500. The real advantage of the faster bike was not so much the maximum power, but that you had enough power to start well down the rev range, and could complete without even considering changing up.

Yeah. I was told, if you're going to do it, get it done. Minimise the time you're exposed/on the 'wrong' side of the road etc.

'ish'

That advice is often taken as meaning 'go as fast as you can't.

But potentially that means that if anything goes wrong you'll have a higher speed differential from the vehicle you're overtaking and travel further before taking any action.

Worst case is that it encourages using smaller gaps with reduced margins.

And worth noting that 'overtaking' is high risk, and one of the three 'gotchas'. RoSPA noted:

" In Clarke et al’s (2004) study, in 16.5% of accidents where the rider was considered partly or fully to blame, the rider was overtaking another vehicle."

Well, yes....but...the advice/training was preceded by all the other assessments prior to making the overtake. Then it was a case of 'get it done' rather than 'go past as fast as you possibly can'.

Just context really.

[mangocrazy]

Yeah. I was told, if you're going to do it, get it done.

Shakespeare, innit?

'If it were done when 'tis done, then 'twere well it were done quickly'...

That Macbeth was a bit of a hoolie, I reckon.

[Horse]

Indeed. But often 'abused' in a similar way to holding position near the centre line in the face of oncoming traffic.

[Horse]

Yeah. I was told, if you're going to do it, get it done.

Shakespeare, innit?

'If it were done when 'tis done, then 'twere well it were done quickly'...

That Macbeth was a bit of a hoolie, I reckon.

The only bit of Shakespeare I remember is the gatekeeper in Macbeth:

"Drink is the great equivicator. It giveth the desire but taketh away the performance."

[Count Steer]

Yeah. I was told, if you're going to do it, get it done.

Shakespeare, innit?

'If it were done when 'tis done, then 'twere well it were done quickly'...

That Macbeth was a bit of a hoolie, I reckon.

Aye. 'Is this an overtaking opportunity I see before me? Come, let me clutchlessly have thee'....which is all well and good until you dump it in Burnham Wood...which appeared to actually approach rather quickly.

[Cousin Jack]

Yeah. I was told, if you're going to do it, get it done.

Shakespeare, innit?

'If it were done when 'tis done, then 'twere well it were done quickly'...

That Macbeth was a bit of a hoolie, I reckon.

The only bit of Shakespeare I remember is the gatekeeper in Macbeth:

"Drink is the great equivicator. It giveth the desire but taketh away the performance."

aka "Brewer's droop"

[mangocrazy]

I did Macbeth for my O-levels. Can still remember bits of it. Favourite is probably

'Light thickens and the crow makes wing to the rooky wood.
Good things of day begin to droop and drowse while night's black agents to their prey do rouse'

I seem to recall Vincent Price reciting that...

[Count Steer]

Yeah. I was told, if you're going to do it, get it done.

Shakespeare, innit?

'If it were done when 'tis done, then 'twere well it were done quickly'...

That Macbeth was a bit of a hoolie, I reckon.

The only bit of Shakespeare I remember is the gatekeeper in Macbeth:

"Drink is the great equivicator. It giveth the desire but taketh away the performance."

We had two versions of the book at school. In one the gatekeeper's speech had been expunged to protect our developing minds. (Our E.Lit teacher was having none of that bolleaux. RIP Jack, the only teacher that changed his car every time the ashtrays were full and who, when we were due to leave said 'Right, you've read all the **** you're 'supposed' to. Now read these' and gave us his recommended book list).

[wheelnut]

'ish'

That advice is often taken as meaning 'go as fast as you can't.

But potentially that means that if anything goes wrong you'll have a higher speed differential from the vehicle you're overtaking and travel further before taking any action.

Worst case is that it encourages using smaller gaps with reduced margins.

And worth noting that 'overtaking' is high risk, and one of the three 'gotchas'. RoSPA noted:

" In Clarke et al’s (2004) study, in 16.5% of accidents where the rider was considered partly or fully to blame, the rider was overtaking another vehicle."

Especially on a multi-vehicle overtake. You’re overtaking 4 cars, move out, accelerate, get past 1 and 2, car 3 decides to pull out to OT car 1 and your speed differential seriously narrows your options.