Everybody’s opinion is worth listening to

Leaving the design of our streets in the hands of just one group of professionals, no matter how well intentioned they may be, is never a good idea, says John Dales

I am afraid to have to admit that I failed to register a formal response to the consultation on the Manual for Streets discussion draft within the official time limit. This was, of course, due to a number of other pressing professional commitments, or possibly my holidays.

There has been surprisingly little debate about the MfS in the press: so far I’ ve noticed only two letters, one of which merely added a few more pointless words to the cul de sac sideshow. The other, however, was from a chap who was very far from gruntled with the draft MfS, appearing to consider it some sort of conspiracy by ‘our planning colleagues’ (for which read ‘those *#@*$%#! planners’ ) to ‘ take over the agenda of road design’ from the ‘we as a profession’ on whose behalf the writer was selflessly raising the cudgels.

This same ‘we as a profession’ was also called to the barricades of road safety auditing, since this is seemingly now under threat from ‘a few planners and architects’. The correspondent also did a neat job of table­ turning, accusing ‘ planners’ of being the real culprits responsible for the ‘ traffic dominated layouts’ for which engineers traditionally get it in the neck.

All of this leads one to assume that the pro­ fession that this particular correspondent considers himself part of is some branch of engineering, or perhaps ‘ engineering’ itself. However, one hopes very much that he doesn’ t speak for it. After all, as a contribution to any debate, ‘it’ s all their fault’ is a rather pitiful shot. We get precisely nowhere worth going when we start pointing fingers at any group of professionals with whom we ourselves (whichever group we belong to) will plainly have to work closely and effectively in order to achieve better outputs.

Concerning the design of streets, their com­ plexity simply doesn’ t allow them to be the province of only one professional discipline. Those that have been designed primarily from the perspective of just one discipline usually fail, or succeed only from that one perspective. It is for this reason that I personally welcome the MfS’ s suggestion that safety audits should be replaced by some form of what it terms a ‘ quality audit’ . This is by no means to say that safety considerations are not very important but rather to say that other considerations ought also to be part of the mix. For, although the correspondent I quote thinks that ‘ a safety audit, if undertaken by a skilled safety engineer, should be quite objective’ , the fact of the matter is that, as one experienced safety engineer said to me, ‘ a safety audit is just one person’s opinion’.

We have simply got to get used to valuing and seeking the opinion of other professionals working in the same field.

We have simply also, it seems to me, got to start thinking more and this is where I fear that the draft MfS risks failing to be the gen­ uine breakthrough for street design that I trust it can yet be. One of the most revealing find­ ings of the research that the MfS team undertook relates to the content of the resi­ dential street design guides produced by many local authorities around the country. One would have thought that these would bring local issues, character and distinctiveness to the fore and yet it was found that, when it came to ‘ the numbers’ , not one of the docu­ ments reviewed departed in any substantive way from those found in Design Bulletin 32. So, for example, stopping site (y) distances for any given design speed are the same the nation over. Not that the DB32 figures them­ selves are law, mind you. But this goes to show quite plainly that, if an ‘ official’ piece of guid­ ance has a number in it, all of us will swallow it whole and question neither how it was derived nor whether it’ s necessarily appropriate for all circumstances.

Some consider that the draft MfS is being progressive in recommending that the y­ dis­ tance for any given design speed should be considerably shorter than the previous ‘ official’ figure. Others, despite the evidence produced by the primary research of the MfS team, seem still to favour the old numbers. A bit like that comfortable pair of slippers, perhaps. However, my fear is that if all the MfS does is state that, for example, the y­ distance for 30mph should now be 40 metres instead of 70 metres, then a new generation of engineers and (yes) planners will simply go around chanting the new figures as their mantra.

How would it be if the MfS simply let its read­ ers know that, according to the research recently undertaken, it is reasonable to consider that reaction times for drivers are in the order of A and deceleration rates for modern vehicles tend to be around B? Then practitioners like our­ selves could use this information to inform our own thinking.At 30mph we might calculate that A and B would mean that an average car driver could bring his/her vehicle to a stop in around 20 metres after seeing a hazard in its path. How much greater than 20 metres we would want to set the y­ distance for a new junction at would then be up to us, taking local and other consid­erations into account.
Do you think you’ re to be trusted to get it right?