Tuesday, 30 June 2009

Appendix : The damning evidence

Much of the evidence in this is due to the expertise of 2 ex engineers in our group - thanks to Peter Stubbs and Duncan Froggatt.

APPENDIX: SPACE response to the Report by Director of Transport and Highways

30mph and lighting?

There is no need for the road between Totley and the new terminus to be subjected to a 30mph speed limit or to be lit. In his informal advice, the Road Safety Officer merely advised that the road should “ideally” be lit. We agree that there should be some lighting of an appropriate kind adjacent to the terminus itself.

However, having decided to install lighting right along the road in the open country to just beyond the terminus, Mr Bann’s officers are claiming that this is necessary together with the associated 30mph speed limit because of restricted sight lines. Their calculations relating to the need to have a 30mph limit and associated lighting are utterly and shockingly wrong. Here is paragraph 3.1 from his report (our bold type):

  • The bus terminus scheme proposals required the provision of a 30mph speed limit in the vicinity of the access/egress to the bus turning area. This was required to comply with safe visibility conditions. The maximum sight line out of the bus turning area is 111 metres. The design criteria guidance used by the Council (and endorsed by the Department for Transport) states that sight lines under 120 metres require a 30 mph speed limit. In order to slow down traffic approaching the site from Derbyshire, a 40 mph buffer zone was proposed and approved by Board in February 2009.

The maximum sightlines (as measured by 3 members, 2 of whom are retired engineers) are:

  • approximately 350 metres from bus turning area North East towards Totley and the severe bends.
  • approximately 180 – 200 metres from bus turning area South West towards Derbyshire and the bend before Dyson’s Brickworks

So Mr Bann’s department have measured the maximum sightline towards Totley at approximately a third the length of its actual measurement and used this to justify the 30 mph limit. The correct sightline length actually complies with a design speed of 50 mph (DfT and Council design criteria). 30 mph is unsafe hardly anyone sticks to it, it feels unnatural and there is now a lot of tailgating and attempts to overtake. Many Totley people feel that, erring on the safe side, considering the gradient, the emerging buses and the severity of the bends, the limit should be 40mph. This is an achievable, enforceable, sensible speed, well within the guidelines, considerably reduced from the previous national limit of 60mph.

Even the sightline towards the bend before the Brickworks is almost twice as long as Mr Bann’s “maximum sightline.” This is mostly within the new 40mph “buffer Zone” - an appropriate limit we feel (although wrongly measured).

There are yet more outrageous errors in calculation and logic in the next paragraph (again – our bold text):

    • There is no Speed Limit Order (SLO) for the 30mph restriction on the newly lit length of road. Under national legislation, if street lighting is introduced on a previously unlit road, then that road is automatically subject to a 30mph restriction. A SLO need only be made if the Highway Authority wishes to introduce a speed limit in excess of 30mph. The minimum length of road covered by a speed limit is 600 metres. The length of road between the recently introduced 30 mph speed limit at the bus turning area entrance/egress and the existing 30 mph limit at Lane Head Road is approx 200 metres. This means that there is insufficient road length to change the speed limit to 40mph between the bus turning area and the existing 30mph speed limit at Lane Head Road.

The length of road between the existing 30 mph at Lane Head Road and the bus turning area is approximately 800 metres – 4 times Mr Bann’s calculation and 200 metres longer than the minimum length needed. Even so, this is nonsense - we would have thought that this length of road could just be added to the new 40mph zone as it is contiguous with it?

Surely the most basic qualities of an engineer should be the ability to measure correctly? Maybe the errors have occurred because the distances were not measured on site but scaled from a map and the wrong scale used?

Para 3.3 of the report refers to the reportable accident record on this stretch of road. Of these 8 accidents, all apart from one, occurred in 2000 and 2001 and occurred because drivers lost control on the bends. In November 2001, chevrons and crash barriers were erected probably the reason why accidents were reduced. The only one since this date – in 2006 – occurred because “the driver took his eyes off road for a split second and crashed into a wall.” So, accidents have been much reduced and it is doubtful whether lighting will now make much difference. Indeed, section of DfT Road Safety Research Report No 100 (Nov 2008) points out that “improving lighting has been shown to result in higher vehicle speed”, so the situation could actually be worsened.

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