Third Bridge – debunking a myth


What is the most famous ancient belief that’s subsequently been disproved?  A flat earth?  Heat coming from caloric?  The existence of aether?  The earth as the centre of the universe?  The guy who sculpted the Forbury Lion killed himself?  Well, it turns out we have a new candidate to top them all: a third Reading bridge would increase traffic in South Oxfordshire.  This long-standing principle has been central to opposition to the new crossing from the north bank for decades, but according to a new report it’s been sensationally disproved. 

Credit to GetReading for unearthing this newly-released report on the “Strategic Outline Business Case” for a third Thames Bridge.  The 67-page document has appeared on Wokingham Council’s website.  It describes the different options that have been considered and simulated using a complex computer model.  Three options were considered: (1) a two-lane bridge, i.e. one lane each direction, (2) the same two-lane bridge but with tolls, and (3) a four-lane bridge split between all-traffic and bus lanes.

Option (1) is deemed to provide by far the most benefit relative to its costs.  GetReading leads with the finding that the toll option would provide the least benefit based on too many people being put off using the bridge by the toll.  This is certainly a really interesting result from the data modelling.  But perhaps they failed to read on to page 45, because this is where the big news lurks:

“The roads in South Oxfordshire crossed by the screenline shown in Figure 4-1 are predicted to carry less traffic across all options apart from the evening peak movement in Option 2”

Screen Shot 2017-10-30 at 20.47.55

So the preferred scheme – option one, a basic bridge for cars – would reduce the volume of traffic crossing the red line on the map above.  Now, I actually put forward a case for why this might happen in my blog last year, where I speculated that Caversham residents (such as myself) might use the new bridge for quick access to the motorway network (I would!) to reach the midlands rather than meandering up to the M40 through South Oxfordshire.  The report’s authors seem surprised by their results:

“The reduction may be due to longer distance traffic diverting away from the area”

They go on:

“Despite the overall reduction in traffic along the South Oxfordshire screenline, some roads forming the screenline are forecast to show a reduction in traffic whereas others show an increase… In absolute terms the differences are relatively low and range between -71 vehicles (B481 between A4130 and Rotherhithe Street, AM peak, Option 3, Southbound) and 34 vehicles (A4074 Red Lane between B471 and Icknield Rd, PM peak, Option 1, Eastbound).”

Then a win for Henley:

“The variations in traffic flows on South Oxfordshire roads are more noticeable in areas located closer to the New Crossing. The scheme is forecast to result in a reduction in traffic on the routes to, from and through Henley-on-Thames, particularly along the A4155 just south of the railway station reaching their highest in AM in Option 1 (-152 vehicles in the northbound direction and -128 vehicles in the southbound direction).”

And nothing doing in Sonning Common:

“The impact of the New Crossing on roads in Sonning Common is mixed with some routes are forecast to show an increase in traffic and with others to show a reduction in traffic. The changes vary across different options and time peaks… To provide an indication of the level of changes, AM Option 1 flow changes around Sonning Common are forecast to range between -17 and 60 vehicles and PM Option 1 flows changes range between -27 and 41 vehicles.”

And finally:

“There is no evidence to suggest that the New Crossing may attract longer distance strategic movements from M40 and M4 to South Oxfordshire highway network.”

GetReading finishes with a “this thing ain’t over”-style quote from Oxfordshire’s leader.  And it isn’t.  The report also provides a cost estimate – £110 million.  That’s going to take more work to secure, and apparently there isn’t even yet the funding in place to continue to work up the design for the scheme.  Then there’s Oxfordshire remaining complaint – the fear of ensuing development north of the river.  But clearly this report takes us a small but important step towards delivering a bridge that could benefit so many people.  Today’s school children learn of the work of Copernicus disproving the Earth’s place at the centre of the universe, and now tomorrow’s can learn of the fine work of “WSP Parsons Brinckerhoff” in debunking the most long-standing local folklore.

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Third Bridge – debunking a myth

9 thoughts on “Third Bridge – debunking a myth

  1. Andrew Taylor says:

    Useful post, thanks. Regarding the last point about South Oxfordshire worrying about development: isn’t it rather ironic that they are happy to support an inappropriate development in Dunsden which would adversely impact on *Reading’s* infrastructure and services, whilst simultaneously opposing a third bridge for fear of…development north of the river?!


    1. Haha, thanks Andrew. I think in fairness South Oxfordshire are strongly opposed to the Dunsden proposal. As I understand it, they were too slow getting their various policy documents signed off, which allowed an opportunist developer an open goal.


  2. I have been in transport one way or another all my life. (76yrs) And MORE than 40yrs ago the planners said we need a third bridge, but, Oxford said they do not want the extra traffic. Has any one in either council ever noticed the amount of traffic that uses the Woodcote/Oxford Road to Bypass the terrible A34 to get to the M40. It costs companies quite a lot for there vehicles to go Via the M4 And A34. The A329 into Reading was built to go across the Thames and straight round the top of Emmer Green, and up grade the rest of the A4074. And the costs keep going up from then, is there no one who will say LETS DO IT.


    1. Thanks Bob. I see some merit in that plan, but it’s just too controversial. The beauty of this current more localised proposal is that it provides all the benefits of taking much of the Caversham-to-M4 traffic out of central Reading without attracting extra longer distance traffic into South Oxfordshire. And it relieves Sonning, and to a lesser extent Henley. This is a plan that can be delivered, and why these findings that there would be a small reduction in traffic in South Oxfordshire is a really important step.


  3. Bob says:

    Interested resident of Sonning Common here.

    This newly released report is not an objective assessment of the pros & cons of the proposed bridge. It is a sales pitch for a new bridge, with data chosen to support its adoption and arguments balanced against the negative aspects to make them seem less important. Like any sales literature, the whole document is designed to make you say “Yes” not “No”. This is clearly indicated in part 3.8.3 which dismisses valid concerns out-of-hand with the platitude that “The concerns of South Oxfordshire DC will be considered and mitigated during the development of the New Crossing”. A tacit admission of concerns existing and a warm fuzzy glow of a suggestion that those concerns are trivial and can be ignored.

    If I cut off your arm and give you two paracetamol for the pain, I have “mitigated” your pain, even if I have done so in a hopelessly insufficient way. There is no reason to assume that the “the concerns of South Oxfordshire DC ” can actually be properly relieved by mitigation measures and as no measured are even alluded to it is impossible to be confident. The report writers are just kicking this into the long grass and hoping no-one notices.

    A quick look at Appendix B to this report instantly shows that Option 1 (the preferred option) is expected to increase traffic between Reading and Sonning Common along the B481 at all times of day (AM peak, inter peak and particularly PM peak) and in both directions. There is a -27 impact (reduction) on traffic leaving Sonning Common along the Rotherfield Peppard road in the PM peak. I think it is reasonable to assume that this simply indicates that some people are expected to stop driving down the Rotherfield Peppard road to use Henley Bridge and instead to pass completely through Sonning Common towards the proposed new bridge, (thus explaining why the traffic both into and out of Sonning Common on the B481 will be adversely affected). These are pretty much exactly the adverse effects that local residents have been concerned about all along.

    You make play of the report’s comments that journey’s across the screenline towards the Northern edge of South Oxfordshire are predicted to drop. Appendix 2 presents data in a way which makes this difficult to check, partly as the screenlines are not actually marked on. None the less I think that one can see a moderate increase in the traffic using the A4074 to travel North/South across that rough line.

    The writer of the report has been unable to offer a reasonable explanation for why traffic across the screenline would decrease in the model, and seems surprised by it. This suggests a problem with the model. I would suspect (maybe wrongly) that the points at which traffic was surveyed for future journey intentions may have all been relatively local and thus the data may be a poor indicator of the travel intentions of people who would actually make these “new” journeys starting further afield. I.e. perhaps they didn’t survey people travelling from Basingstoke or Bucklebury, or Didcot and these are the people who might make a “new” Journey across the screenline to use the proposed bridge.

    I am almost certainly being a NIMBY in my attitude towards this plan but I can’t apologise for wanting to protect my family’s living environment from negative traffic impacts. Perhaps those in favour of the bridge could be similarly honest and recognise that they have a self-interested desire to improve their own environment by shifting traffic volume away from their own homes in e.g. Caversham. They don’t really care what happens to that traffic once it is out of their neighborhood.

    Liked by 1 person

    1. Thanks Bob for your detailed and honest response. It’s exactly the kind of contribution I’m keen to see on my articles so thank you for taking the time to share your view, even though it’s not exactly the same as mine!

      A couple of points. I think the report (and I) acknowledge there are localised increases and decreases in traffic as journeys are reconfigured as a result of the extra link in the road network. But I think that’s inevitable from any change to any road network. I think “mitigation” means ensuring no major new bottlenecks are created, and that the scale of any localised impacts is low (not zero). The magnitude of the changes in South Oxfordshire doesn’t sound large, although I’d be interested to see them expressed as a percentage of current levels.

      Regarding your point about supporters of the scheme, I can only speak for myself. I live just off Caversham Park Road, which would see the biggest increase in traffic. It’s currently a surprisingly quiet road given its layout as a main road with barriered pavements and underpasses etc. It would become a busier road. So I lose on traffic and noise. I gain from faster access to the motorway network.

      But the gain I care most about is the wider benefit for Reading, which I hope you can believe is genuine given the time I spend blogging about the town. Moving existing “through” traffic around the edge of town would ease the chronic congestion in the town centre (IDR). Even if you accept the Green argument that new journeys will fill the space, those would be far more likely to be using the town centre as a destination – people spending their money here, providing demand to underpin a wider variety of shops/leisure in the town centre, giving Reading the vitality I want to see us enjoy.


    2. dangrey says:

      Quite simply, transport consultants know that if they produce a report which shows an increase in traffic from a development they won’t get a contract from that client again. That’s why developments always produce much more traffic than they were ‘forecast’ to. You’ll only see academic papers pointing out the causal link between development and increased traffic, congestion, and pollution.


      1. You’re probably right to be cynical about official reports. But in this case, the result is strikingly contrary to received wisdom so I believe it would remain significant even if it’s been impacted by some element of bias (subconscious or otherwise).


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