Peyote wrote:
But I can't understand why putting the bollards up would give the driver less time to brake? The pedestrians aren't going to walk faster because of the presence of the bollards, and if anything the driver would be travelling slower (to get through the bollards) so this would provide more time to brake, and less effort to brake to a suitable level. Wouldn't it?
I think the line of reasoning being followed by Pete is something like this:
On a normal turning into/out of a side road, you can usually make the turn without getting too close to the pavement. On one of these narrowed junctions, you have no choice but to get within inches of the pavement. If a pedestrian is stood at the kerbside on a normal junction and steps into the road without looking (or despite looking, seeing you, and then deciding to walk in front of you anyway and to hell with right of way or any other quaint concept like that), chances are they'll still have to cover a foot or so of road before they pass into your path. If a pedestrian is stood at the kerbside on a narrowed junction and steps out, they are almost certainly going to be right in your path as soon as they start moving forwards.
If these bollards are placed right at the junction rather than being set back into the side road, then they provide a minimal additional incentive to slow down beyond that which is already offered by the realisation that you're heading towards a give way/stop line and a major road - you may need to slow down marginally sooner to begin negotiating the bollarded area, but you're not likely to be driving along a significant stretch of the road any slower than you would have done in the absence of the bollards.
By extending the pavement out towards the centre of the road and installing bollards which may give the impression that this particular bit of pavement is better protected against vehicle incursion than any other bit of pavement in the vicinity, you may encourage pedestrians to alter their behaviour at such junctions - the extended pavement can give the illusion that it's safe to continue walking at normal pace beyond the point at which you'd normally be slowing down to look for traffic, and the bollards may give the illusion that vehicles will definitely be moving more slowly than at a normal junction (or may even, from some angles, give the impression that the junction is closed to vehicular traffic, leading to pedestrians not bothering to look for traffic at all).
Sticking additional obstacles at a junction makes the driver concentrate on not hitting the obstacles, when they'd normally be concentrating on looking out for other road users (which includes pedestrians).
I'm exceptionally wary of crossing a road in the vicinity of a speed camera, because I know that a significant number of drivers will be paying at least some attention to the camera, taking away from the amount of attention they're paying to looking out for pedestrians trying to cross the road. In the same way, I'm also very wary of crossing a road in the vicinity of artificially narrowed sections, because the extended kerbs, bollards and other street furniture used to create such sections are going to have pretty much the same effect on driver attention as the camera.