Sunday, 19 January 2020

Terrible Barrier

Yesterday, I combined an invitation to be a panelist at Camcycle's AGM with a bit of a mooch around Cambridge city centre and a mini infrastructure safari.

I'm hoping to be back for a proper infrastructure safari later this year and so this week, I'm going to concentrate on one thing and that's the new counter terrorism installation at Kings Parade in the historic heart of Cambridge.

It's a location which has been a concern from a counter terrorism point of view for some time. We've seen the incidents where vehicles have been driven into crowds of people and Kings Parade is a popular tourist spot for tourists taking photos of Kings College as well as enjoying the beauty of the street.

The problem is, Kings Parade is also one of the busiest streets in the city for cycle traffic and so one would have thought that this would be taken into account in designing the installation. Sadly, it seems that cycling and walking have been ignored.


The barrier has been installed here and is a familiar collection of oval (on plan) concrete-filled shell blocks (called "barges" by the manufacturer) combined with a central openable gate. The barges weight about 3 tonnes each. The installation is designed to stop someone driving a vehicle into a crowd - know as "hostile vehicle mitigation" (HVM). 

The system uses its mass and friction with the ground to prevent someone driving a vehicle through, although the units will be moved in the event of a high speed collision - the point is to dissipate energy and bring a vehicle to a halt, probably with extreme damage. The photo above shows a pair of barges either side of the gate (for occasional access I assume). The barges are connected and so there's a lot of mass there. There are two individually placed barges on each side of the gate assembly which are offset from each other but not connected. 

The street has a wide footway on the eastern side of the street and a narrower one on the west side; a fairly narrow carriageway and a loading bay (the cobbled are to the left of the carriageway in the photograph). The installation of the gate straddles the carriageway and the loading bay (which turns into a hard strip) with an area left for cycle traffic to the western side of the carriageway. The footway width on each side is maintained, albeit with two barges each.


The photograph above shows a closer view of the cycle side of the installation which has a pretty narrow gap between the barges - so narrow in fact that people have to cycle through in single file. That wouldn't be so bad, except it's a gap for two-way cycle traffic!


On close up, it's even worse. Almost half the space is a granite sett channel (with a slot drain in centre) and a kerb with a slight upstand. Granite can be very slippery to cycle over and the design means that every person who cycles through in damp or frosty conditions is at risk of falling off their cycle - right into the barges. While I was on site, I saw a few people cycling and one motorcyclist across the footway.

Two-way cycling is not possible and so people have to give way to each other. Although people cycling are very adept at adjusting their speed and direction, this pinch point slows progress and creates the potential for head on collisions - here's me cycling through;


I had a look at about 10.30 on a Saturday morning - imagine the chaos on a weekday peak - it really is so poorly thought out.

Just beyond the barrier to the south, there is a junction where Kings Parade turns into Trumpington Street with Bene't Street off to the east. Trumpington Street has motor traffic restrictions (signs) from the south from it's junction with Silver Street, but of course any would-be terrorist isn't bothered about traffic signs. In theory, therefore, someone could drive about 160m along Trumpington Street where there are plenty of people milling about.

The area to the north of the barrier is better protected. Kings Parade becomes Senate House Hill where there is a rising bollard which appears to be used to permit emergency access; there's probably more people milling around to the north of the barrier. 

The wider problem the city centre has from a counter terrorism point of view is that although there's a large pedestrian (and cycling) zone, there is an "except access" exemption and frankly anywhere could be a target. There will be analysis to demonstrate that Kings Parade is a site of concern, but it seems to me that a larger review is needed. As far as the current barriers go, they really need to be changed.

It's a wider issue for the UK. We keep rolling out this stuff in response to concerns about terrorism, but in the process we make day-to-day access for walking and cycling more awkward as well as helping to clutter our streets. In many ways, the terrorists have already won.

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