Has closing Hammersmith Bridge really improved London’s air quality?

Hammersmith Bridge. Image: Getty.

Hammersmith Bridge, opened in 1887, was indefinitely closed on the 10th of April 2019 as a result of “critical faults” found by safety sensors. It is currently closed to all motorists including buses but remains open to pedestrians and cyclists. The final plan has not yet been decided but it is estimated that the repair costs will be at least £40m.

Consequently, some argue that the bridge should be closed to motorists for good. However, Transport for London does not want to “lose” the bridge, so has pledged to spend £25m despite it being the responsibility of the council. Steve Cowan, Labour leader of Hammersmith & Fulham council, announced that the bridge “would reopen to motorised traffic within three years”.

Hammersmith has persistently had air quality problems and has the eighth highest percentage of early deaths attributable to air pollution in London, according to a report by King’s College London. It has been a designated air quality management area since 2010. Understandably, residents were therefore concerned about the increased congestion leading to higher levels of pollution.

We therefore decided to investigate if we could find any effect on air quality due to the closure of the bridge. For our investigation, we primarily used data from three continuous Air Quality Monitoring Stations in the Borough of Hammersmith and Fulham and Wandsworth. Their locations are shown below in red.

Pollution levels are measured hourly. We used the NO2 results, as this is both one of the main pollutants released by cars and is almost entirely released by cars.

Looking first at Hammersmith Town Centre, there is a general decline in the level of pollutants in the town centre. However, this decline began before the closure of the bridge and in fact was sharper before it.

Does this mean that there is cause for concern? Is the closure perhaps retarding air quality improvements? Well, the data demonstrates that the level of pollutants is lower, peaks less frequently. and when it does peak it is generally lower than before the closure. The standard deviation before the closure was 75.1, whilst after it is 54.8. This significant change suggests that the closure of the bridge has had an effect on pollutants in Hammersmith town centre.

To a lesser extent, the same trends can be seen in Shepherd’s Bush. There is a slight overall decline. However, as in Hammersmith, the decline started before the closure and has since become more gradual. The maximum levels per day also decreased and anomalously high results were also less frequent.

However, the change in standard deviation was less significant in Shepherd’s Bush (30.2 before the closure and 21.2 after) most likely due to Shepherd’s Bush being significantly further from the bridge.

On the other side of the Bridge in Putney, the same trends can be identified although they too are less significant than the data from Hammersmith Town Centre probably owing to the further distance. However, as the level of pollution has not increased as a result of additional congestion caused by the closure there is no apparent environmental damage. In fact, if the increased congestion or overlong diversions have caused residents to use other methods of transport this could explain the lower maximum results, indicating that the closure has actually had a slight beneficial impact on air quality in Hammersmith.

It seems that, at least whilst the bridge is closed, some people are choosing more environmentally friendly modes of transports knowingly or otherwise. Will this change people’s habits for good? It’s hard to say. But maybe this is a chance to improve public transport and the liveability of surrounding streets so that congestion can be reduced for good and the good people of Hammersmith can breathe cleaner air.

Eletta Rainsford is working with Create Streets before completing her studies in maths and statistics. This is her first published article.


 

 
 
 
 

London’s rail and tube map is out of control

Aaaaaargh. Image: Getty.

The geographical limits of London’s official rail maps have always been slightly arbitrary. Far-flung commuter towns like Amersham, Chesham and Epping are all on there, because they have tube stations. Meanwhile, places like Esher or Walton-on-Thames – much closer to the city proper, inside the M25, and a contiguous part of the built up area – aren’t, because they fall outside the Greater London and aren’t served by Transport for London (TfL) services. This is pretty aggravating, but we are where we are.

But then a few years ago, TfL decided to show more non-London services on its combined Tube & Rail Map. It started with a few stations slightly outside the city limits, but where you could you use your Oyster card. Then said card started being accepted at Gatwick Airport station – and so, since how to get to a major airport is a fairly useful piece of information to impart to passengers, TfL’s cartographers added that line too, even though it meant including stations bloody miles away.

And now the latest version seems to have cast all logic to the wind. Look at this:

Oh, no. Click to expand. Image: TfL.

The logic for including the line to Reading is that it’s now served by TfL Rail, a route which will be part of the Elizabeth Line/Crossrail, when they eventually, finally happen. But you can tell something’s gone wrong here from the fact that showing the route, to a town which is well known for being directly west of London, requires an awkward right-angle which makes it look like the line turns north, presumably because otherwise there’d be no way of showing it on the map.

What’s more, this means that a station 36 miles from central London gets to be on the map, while Esher – barely a third of that distance out – doesn’t. Nor does Windsor & Eton Central, because it’s served by a branchline from Slough rather than TfL Rail trains, even though as a fairly major tourist destination it’d probably be the sort of place that at least some users of this map might want to know how to get to.

There’s more. Luton Airport Parkway is now on the map, presumably on the basis that Gatwick is. But that station doesn’t accept Oyster cards yet, so you get this:

Gah. Click to expand. Image: TfL.

There’s a line, incidentally, between Watford Junction and St Albans Abbey, which is just down the road from St Albans City. Is that line shown on the map? No it is not.

Also not shown on the map: either Luton itself, just one stop up the line from Luton Airport Parkway, or Stansted Airport, even though it’s an airport and not much further out than places which are on the map. Somewhere that is, however, is Welwyn Garden City, which doesn’t accept Oyster, isn’t served by TfL trains and also – this feels important – isn’t an airport.

And meanwhile a large chunk of Surrey suburbia inside the M25 isn’t shown, even though it must have a greater claim to be a part of London’s rail network than bloody Reading.

The result of all these decisions is that the map covers an entirely baffling area whose shape makes no sense whatsoever. Here’s an extremely rough map:

Just, what? Image: Google Maps/CityMetric.

I mean that’s just ridiculous isn’t it.

While we’re at it: the latest version shows the piers from which you can get boats on the Thames. Except for when it doesn’t because they’re not near a station – for example, Greenland Pier, just across the Thames to the west of the Isle of Dogs, shown here with CityMetric’s usual artistic flair.

Spot the missing pier. You can’t, because it’s missing. Image: TfL/CityMetric.

I’m sure there must be a logic to all of this. It’s just that I fear the logic is “what makes life easier for the TfL cartography team” rather than “what is actually valuable information for London’s rail passengers”.

And don’t even get me started on this monstrosity.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.