Measuring Breakaway Gaps

[Waterloo Sunrise]

Just wondering if anyone has a definitive reason why these should be measured in time, or distance?

At the moment they're measured in time, meaning they avoid being perverted by the parcours. However they are entirely beholden to the relative speeds, so if the peloton starts to ride the measured gap instantly drops significantly.

By contrast, measuring them on distance can lead to issues with the parcours (when the road starts to point up, the gap drops) but avoids the silly swings in 'gap' created by changing relative speeds.

Personally I feel distance gives a more objective measure. Using time introduces a second variable, with the only 'benefit' of making the inevitable variablility in measured gap the result of a factor most people ignore, rather than a factor which is known and anyone with half a brain can comprehend.

 

[Bernie's eyesore]

Obviously they should be measured by time.

 

[Waterloo Sunrise]

Obviously they should be measured by time.

Glad that's settled then.

 

[cineteq]

Think of this: How can you measure distance at any given time and be accurate?

 

[Ferminal]

I agree distance would make a bit of sense. But in stage races you need to know the time if there is someone GC relevant outside the main group. You would either have to use time only or use distance but provide time gaps when required.

In one day races time doesn't mean anything, distance would probably be better.

Think of this: How can you measure distance at any given time and be accurate?

No different to time, in fact simpler, as there's no speed to consider. Fixed point timing is different of course.

 

[Buffalo Soldier]

You make it sound too complicate.
They just show how much time has passed since the leaders were at the place the peloton is now?

No need to bring up relative speeds?

 

[Waterloo Sunrise]

You make it sound too complicate.
They just show how much time has passed since the leaders were at the place the peloton is now?

No need to bring up relative speeds?

breakaway 1KM ahead of peloton, both doing 20KPH, the time gap is 3 minutes.

Then both breakaway and peloton increase speed to 40kph. The time measured gap is halved, which should mean the breakaway is now in a much worse position. Except they clearly aren't.

 

[Waterloo Sunrise]

Just over 100km still to go and the gap is around 5:30 to the 14 riders up the road.

That information is actually quite difficult to understand, using 2 seperate metrics.

Why not tell me how far ahead, and how far to go.

Or if time is a valid measure, why not tell me how far to go in time. (Of course, thinking through the implications of that should make the downsides of measuring in time clear to anyone who hasn't yet caught on.)

 

[issoisso]

This reminds me of the time that moron, the portuguese eurosport commentator Paulo Martins, kept insisting that the 6 minute gap between Sastre and Landis wasn't "the true gap" because Landis was going downhill and therefore faster, while Sastre was still climbing and therefore slower. He insisted that once Sastre started descending, the gap would be about 2 or 3 minutes.

Mind you, he was a professional cyclist for several years, not some random guy pulled from whatever other sport to commentate.

The most hilarious part was when, after about 2 minutes of being told the polite version of "you're an idiot" by the co-commentator, he realized how stupid what he had said was and his voice tone completely changed.

Not that he admitted to being wrong. Being Paulo Martins, he refused to ever do that.

Apologies for the off-topic

 

[Libertine Seguros]

breakaway 1KM ahead of peloton, both doing 20KPH, the time gap is 3 minutes.

Then both breakaway and peloton increase speed to 40kph. The time measured gap is halved, which should mean the breakaway is now in a much worse position. Except they clearly aren't.

But if the breakaway and the péloton have both increased their speed, the time gap will be constant, especially where they use GPS to give us real time updates on it.

On the other hand, on a climb, the distance may be very small, then suddenly shoot out by miles when the breakaway start descending, but the péloton is still climbing, whereas time-wise it will still be the same because in that 3 minutes' time the péloton will be going faster.

Like when you watch motor racing, they measure the distance between vehicles in time. As cars slow down for a hairpin, the distance between the vehicles becomes smaller, as when one car is braking for the hairpin, the other is still accelerating down the straight. But the car that reached the hairpin first then re-opens the distance between them because they can accelerate first, and so while the distance between the two cars has fluctuated massively, the time gap has remained more or less constant (allowing for differences in ability to take the corner, of course).

Cycling is just like that, only rather than being for a second or two round a corner, it's for 45 minutes up a mountainside.

 

[Caruut]

Just wondering if anyone has a definitive reason why these should be measured in time, or distance?

At the moment they're measured in time, meaning they avoid being perverted by the parcours. However they are entirely beholden to the relative speeds, so if the peloton starts to ride the measured gap instantly drops significantly.

By contrast, measuring them on distance can lead to issues with the parcours (when the road starts to point up, the gap drops) but avoids the silly swings in 'gap' created by changing relative speeds.

Personally I feel distance gives a more objective measure. Using time introduces a second variable, with the only 'benefit' of making the inevitable variablility in measured gap the result of a factor most people ignore, rather than a factor which is known and anyone with half a brain can comprehend.

Relative speed has absolutely nothing to do with the measured time gaps. Time gaps are a measure of the time elapsed since a group was in the position another group (probably the peloton) is now in. They have nothing to do with the relative speed.

Distance is, as you say, completely dependent on the parcours. The time gap is great in that you can essentially see if they are being brought back, staying stable or gaining. With distance you really have to know exactly what the gradient both groups are is and have enough understanding of physics to work out exactly what that means.

Perhaps both should be quoted, but time is so much more relevant.

 

[Waterloo Sunrise]

But if the breakaway and the péloton have both increased their speed, the time gap will be constant, especially where they use GPS to give us real time updates on it.

On the other hand, on a climb, the distance may be very small, then suddenly shoot out by miles when the breakaway start descending, but the péloton is still climbing, whereas time-wise it will still be the same because in that 3 minutes' time the péloton will be going faster.

Like when you watch motor racing, they measure the distance between vehicles in time. As cars slow down for a hairpin, the distance between the vehicles becomes smaller, as when one car is braking for the hairpin, the other is still accelerating down the straight. But the car that reached the hairpin first then re-opens the distance between them because they can accelerate first, and so while the distance between the two cars has fluctuated massively, the time gap has remained more or less constant (allowing for differences in ability to take the corner, of course).

Cycling is just like that, only rather than being for a second or two round a corner, it's for 45 minutes up a mountainside.

Why would the time gap be constant?

They both increased their speed equally, at the same moment, so the distance between them would remain the same. The time gap is then simply the time taken for the 2nd group to cover that distance, which by a doubling of speed, has halved.

Both metrics have incomplete information to properly understand the situation. But with the distance measure, the information you lack is available on a profile. The hidden information is more subtle, and thus easier to completely ignore, when measuring time.

 

[Waterloo Sunrise]

Relative speed has absolutely nothing to do with the measured time gaps. Time gaps are a measure of the time elapsed since a group was in the position another group (probably the peloton) is now in. They have nothing to do with the relative speed.

Distance is, as you say, completely dependent on the parcours. The time gap is great in that you can essentially see if they are being brought back, staying stable or gaining. With distance you really have to know exactly what the gradient both groups are is and have enough understanding of physics to work out exactly what that means.

Perhaps both should be quoted, but time is so much more relevant.

Apologies, I should have said peloton speed.

The reason I brought this up is the frequent site of someone saying the gap has tumbled in a sprint stage when the peloton wakes up and shifts from 35kph to 45kph. You get instantaneous drops in gap and many people don't seem to have realised that it is largely a figment of the measurement method rather than a genuine phenomena.

 

[El Pistolero]

Erm, no. They use the time difference between the 2 motors.

 

[Libertine Seguros]

Why would the time gap be constant?

They both increased their speed equally, at the same moment, so the distance between them would remain the same. The time gap is then simply the time taken for the 2nd group to cover that distance, which by a doubling of speed, has halved.

Both metrics have incomplete information to properly understand the situation. But with the distance measure, the information you lack is available on a profile. The hidden information is more subtle, and thus easier to completely ignore, when measuring time.

How often does the speed increase occur concurrently?

The case for distance would actually have been stronger in days gone by, whereas now that we have access to all kinds of data via GPS and so on, time gaps can be continuously updated.

The other factor, of course, is that cycling races are not sportscar events; they do not run to distance over a set period; they run to time over a set course. As the gaps between riders are measured in time, it is better both for the riders and the viewers trying to understand the race if the metric used to measure the gap between riders is the same one the race results will be judged on.

After all, if a rider in the péloton has a 1 minute lead over a rider in the breakaway, he or she can tell immediately if the gap is cited at 1 minute that they must up their pace or they will lose the race. If they are cited that the rider in the break is X amount of metres ahead of them, they (and the viewers at home as well) need to know the relative speeds of the two groups in order to calculate what the implication of the difference would be.

 

[Caruut]

breakaway 1KM ahead of peloton, both doing 20KPH, the time gap is 3 minutes.

Then both breakaway and peloton increase speed to 40kph. The time measured gap is halved, which should mean the breakaway is now in a much worse position. Except they clearly aren't.

Nearly. Say the breakaway is 10km ahead on dead flat ground, for argument's sake, let's have the break at 100km in and the peloton at 90km in, and they're both going 20km/h.

So the break completes the 10km between 90km and 100km at 20km/h, so it takes them 30 minutes. Now suppose that as the break go over the 100km point (and the peloton 90km to go), they both accelerate to 40km/h. Then the peloton completes that 10km in just 15 minutes.

So, your reasoning is almost correct, but they are actually in a worse position than they were - the reason the time gap decreases is because the peloton has raced a particular section faster than they have. That is being genuinely worse off.

 

[Caruut]

Apologies, I should have said peloton speed.

The reason I brought this up is the frequent site of someone saying the gap has tumbled in a sprint stage when the peloton wakes up and shifts from 35kph to 45kph. You get instantaneous drops in gap and many people don't seem to have realised that it is largely a figment of the measurement method rather than a genuine phenomena.

No, the drop in gap is not instantaneous. The update in gap size may lead to an instantaneous drop, and poor measuring (like with Iglinsky v Nibali at LBL) may lead to sudden drops, but it is nothing to do with the physics of the situation. The figment is in your imagination.

 

[Waterloo Sunrise]

How often does the speed increase occur concurrently?

It's a thought experiment to illustrate a point - the fact remains that for point of time changes, the breakaway is powerless to affect the measured gap whilst the peloton can vary it just as much as it can vary its speed

The case for distance would actually have been stronger in days gone by, whereas now that we have access to all kinds of data via GPS and so on, time gaps can be continuously updated.

Quite the opposite. It is only through GPS that distance even becomes feasible. And the more frequently you update the time gap, the more random it will appear. The fact it is updated relatively infrequently and so the speed impact is muted is actually a strength for measuring in time

The other factor, of course, is that cycling races are not sportscar events; they do not run to distance over a set period; they run to time over a set course. As the gaps between riders are measured in time, it is better both for the riders and the viewers trying to understand the race if the metric used to measure the gap between riders is the same one the race results will be judged on.

If you are arguing for consistency of metrics aiding comprehensibility, why do we judge the race left to run in distance but the gap in time?

After all, if a rider in the péloton has a 1 minute lead over a rider in the breakaway, he or she can tell immediately if the gap is cited at 1 minute that they must up their pace or they will lose the race. If they are cited that the rider in the break is X amount of metres ahead of them, they (and the viewers at home as well) need to know the relative speeds of the two groups in order to calculate what the implication of the difference would be.

Yes, there is missing information in both metrics - I am arguing in a contrarian fashon as although time is simpler, it actually hides information which is more difficult to take account of, meaning people 99% of the time ignore those factors. By contrast distance would absolutely require people to think through the information in a wider context

I don't seriously suggest this should be switched over, but I do think it's an interested topic to think through.

 

[Waterloo Sunrise]

No, the drop in gap is not instantaneous. The update in gap size may lead to an instantaneous drop, and poor measuring (like with Iglinsky v Nibali at LBL) may lead to sudden drops, but it is nothing to do with the physics of the situation. The figment is in your imagination.

You are conflating the measured metric with the reality.

The gap drop is instantaneous if you genuinely think the gap consists of time.

There is no gap drop whatsoever at the margin, if you think the gap consists of distance.

 

[Buffalo Soldier]

Why would the time gap be constant?

They both increased their speed equally, at the same moment, so the distance between them would remain the same. The time gap is then simply the time taken for the 2nd group to cover that distance, which by a doubling of speed, has halved.

You are using a bad example. Normally groups don't change their speed drastically at the same moment but at the same location on the course (climbing, descending, wind,...). So time gap will stay the same, while distance will change.
Time is a much more solid measurement

 

[Waterloo Sunrise]

Nearly. Say the breakaway is 10km ahead on dead flat ground, for argument's sake, let's have the break at 100km in and the peloton at 90km in, and they're both going 20km/h.

So the break completes the 10km between 90km and 100km at 20km/h, so it takes them 30 minutes. Now suppose that as the break go over the 100km point (and the peloton 90km to go), they both accelerate to 40km/h. Then the peloton completes that 10km in just 15 minutes.

So, your reasoning is almost correct, but they are actually in a worse position than they were - the reason the time gap decreases is because the peloton has raced a particular section faster than they have. That is being genuinely worse off.

The thought experiment is much purer if you think of an infinite length race, but if you want to introduce distance I can happily argue the other way.

After the instantaneous speed change occurs, the time to complete the race has halved. The measured time gap as halved. No real difference.

If however I start to conflate the 2 measures as you do, I could argue...

The time to complete has halved. The distance between is the same. Therefore my gap for racing purposes has doubled.

 

[Waterloo Sunrise]

You are using a bad example. Normally groups don't change their speed drastically at the same moment but at the same location on the course (climbing, descending, wind,...). So time gap will stay the same, while distance will change.
Time is a much more solid measurement

I'm using an extreme example to make the situation easy to understand. If I were to use racing scenarios the same principles hold, but they are much more difficult to pick apart.

 

[Caruut]

You are conflating the measured metric with the reality.

The gap drop is instantaneous if you genuinely think the gap consists of time.

There is no gap drop whatsoever at the margin, if you think the gap consists of distance.

This is just gibberish.

If both groups accelerate at the same time, then one group races a section faster than the other did. So the reason the time gap decreases is because, well, it should do. There is no intrinsic "time difference" between the two groups. The time difference is purely the time taken between two different groups passing the same point.

 

[cineteq]

I don't seriously suggest this should be switched over, but I do think it's an interested topic to think through.

Both time and distance can be used as reference, especially with the arrive of GPS. I don't think one is better than the other. Time was the easy to measure between two riders/groups and thus it became the de-facto measurement. People are used to, thus it won't be changed.

 

[Waterloo Sunrise]

This is just gibberish.

If both groups accelerate at the same time, then one group races a section faster than the other did. So the reason the time gap decreases is because, well, it should do. There is no intrinsic "time difference" between the two groups. The time difference is purely the time taken between two different groups passing the same point.

Two objects a fixed distance apart and always moving at the same speed are never more or less likely to catch each other, regardless of their shared speed.