A quick Google finds the Government's rules for the installation fo rising
bollards, from which it appears that those in the video's are illegal on two
counts:
http://www.dft.gov.uk/stellent/groups/dft_roads/documents/page/dft_roads_504750-01.hcsp#TopOfPage
"Rising bollards should not normally be sited close to or at signalled
junctions or pedestrian crossings."
These are clearly on pedestrian crossings, presumably this rule is precisely
because a car doesn't always crash in a straight line...
"Whilst most applications will be to enable the passage of one vehicle at a
time, there will be instances where two or more vehicles attempt to pass
through in close succession. The system should ensure that bollards cannot
rise beneath a vehicle because of the danger this would create. It is better
to risk a certain amount of violation by "tailgating" vehicles, rather that
put road users at risk."
These don't have any system to ensure they can't rise under vehicles as the
videos clearly show them doing so. My guess is they've twisted the meaning
of this rule to be 'must top rising if a vehicle passes over' which they do
but is nothing like the same thing. To comply they should have a sensor in
the road to detect a car that's close enough to have them rise underneath
it, which would allow a certain amount of violation as acknowledged in the
rule. Of course once people were wise they could 'convoy' behind a bus, so
this Council has simply ignored the rule it doesn't like, something which
should leave them wide open to being sued.
Another point is that, although the bollards have reflective tips many cars
have restricted views of the few metres of road surface immediately in front
of them so if the bollards start to rise fairly close to the car will never
be seen.
Greg