_ambigu0us_

> If you make the pedal more sensitive (increase the resulting travel per pedal press) you'll make it harder to apply a precise amount of braking power which doesn't sound like a nice feature.

If you've tried hopping in a car from the past few years after driving a much older car you (and you passengers) will have probably noticed this! It's very common in modern cars to have much shorter brake pedal travel, so what would bring you to a gentle stop in an older car will be somewhat more abrupt in a modern car.

This is achieved by having a shorter travel pedal, which is then heavily assisted by the brake servos so it is not horribly heavy to apply. This is nominally for safety's sake, as it reduces the time between seeing a obstacle and the brakes being fully applied. And since all recent cars have anti-lock braking and stability systems it doesn't matter so much if the driver can't control the braking pressure quite as precisely.

> I suppose you could have a more clever system that would move the brake faster until it touches the disc and then behave normally but I suppose that for such a critical system constructors and regulators are very conservative.

Exactly, as I mentioned to the other commenter, it's preferable to have a simple, non powered mechanical system in place to stop the car in the event of bad things happening. Adding extra bits to this system, with the vast R+D cost involved, for marginal increases in fuel economy would be hard to justify for most car manufacturers (especially since the fuel economy saving would benefit the users pockets, not theirs).

It's an interesting one certainly, it sort of comes down to mechanics at the end of the day. In the event of a catastrophic, complete electrical/engine failure, the driver needs to be able to apply enough braking force to stop the car in a sensible distance using their leg muscles. This places an limit on the travel distance of the pads for a full press of the pedal.

Indeed, most cars use a servo that uses vacuum 'pressure' harvested from the engine to assist with braking and reduce the amount of effort the driver needs to expend. However, you can still brake with a non-functioning servo, all be it with a much reduced braking performance.

It's a similar reason why even very modern cars (bar a few, the Infiniti Q50 being one) still use direct mechanical linkages (heavily assisted in many cases) for steering, despite the steering rack, column and rods taking up room and complicating engine bay arrangements. If it all goes really wrong, you need to be able to steer and stop the car.

I did not know that term, thanks!

In car braking systems the pedal movement from depressed to pressed corresponds to a very small (<1mm) pad movement. The pad is just touching when the brake when the pedal is not pressed, and pressing the pedal forces the pad and caliper together, increasing friction. Depressing the pedal does not withdraw the pad.

With the brake cylinder fully compressed (as they did for the test), it requires several full pumps of the pedal to bring the pad into contact with the disk. This increases braking distance, which is generally considered a bad thing.

My favorite local junctions is the magic roundabout in Hemel Hempstead, UK [1]. A traffic circle (roundabout with traffic lights) would have also worked for this junction, but instead they used a ring of mini roundabouts, one placed at each entrance/exit road, connected to one another by short dual carriageway sections.

This allows for traffic to flow both ways around the circle, while forcing drivers on the "roundabout" to slow down to navigate the mini roundabouts, while not forcing people to stop completely for lights. In practice it works incredibly well, maintaining a steady flow of traffic even under heavy congestion. IMO it works far better than a controlled roundabout, and it a lot more fun!

It's also a favorite for driving test examiners...

[1] https://www.google.co.uk/maps/place/Hemel+Hempstead,+Hertfor...

Barnes Wallis' Tallboy[1] was a 5 ton bomb designed to be dropped from a high altitude and penetrate deep underground. Upon detonation at the correct depth it could create a large crater, up to 100ft deep and 80ft across, which was identified as being useful for attacking railway targets and airstrips, as repair of these craters was time consuming. Combined with the specialised bomb sights used by the squadron who dropped the Tallboys, successfully bombing a small target such as a viaduct or railway line was doable.

However this bomb wasn't used before June '44, when most of the death camps were closed or closing, and the short supply of Tallboys meant that they were exclusively used for targets of high military importance.

1. http://en.wikipedia.org/wiki/Tallboy_%28bomb%29