TfL urged to be admit the full extent of traffic delays that CS9 would cause

A local resident John Griffiths says Transport for London has sort to play down the extent that the Cycle Superhighway scheme though Hammersmith would cause in increased journey times. Griffiths has raised concerns after studying TfL’s own modelling – on both the CS9 scheme and their Hammersmith Gyratory proposals.

TfL says:

“On the Gyratory proposals The traffic modelling analysis looks at journey times at the busiest hour in the morning and evening peaks. The most notable increases in journey times will be for traffic approaching Hammersmith gyratory from Fulham Palace Road in the evening peak, which may experience an average journey time increase of up to a minute and a half.”

However Griffiths adds:

“Now this is the extra time taken only to traverse the gyratory. For traffic in a queue it will be much longer.

Looking at the information given in the summary results  

Fulham Palace Rd to Shepherds Bush Rd / PM traffic

Current journey time                       2-3 min

Future modelled journey time        4-5 min

Future – Current                              60-90 sec

Let us take the average current journey time as            2.5 minutes

And the average future journey time as                          4.5 minutes.

The ratio of the two is 4.5/2.5 = 1.8, that is an 80% increase in the journey time across the gyratory.

However that is not the total extra journey time if there is a queue to enter the gyratory. Traffic is taking 80% longer to get through the gyratory. So a vehicle in a queue of any given length will now take 80% longer to reach the head of the queue.

So a vehicle in a queue that might now take say 20 minutes to reach the gyratory will in future take about 35 minutes.

A further effect is that as vehicles are being removed more slowly from the head of the queue, the queue in future will be longer if vehicles are arriving at the same rate at the back of the queue.

From the same summary results chart for PM traffic

Hammersmith Rd to King Street

Current journey time                       2-3 min

Future modelled journey time        3-4 min          

Future – Current                              31 – 60 sec

Let us take the average current journey time as 2.5 min

And the average future journey time as 3.5 minutes.

The ratio of the two is 3.5/2.5 = 1.4, that is an 40% increase in the journey time across the gyratory.

Again for any queue in Hammersmith Rd it will take 40% longer to reach the head of the queue.”

So far as the CS9 proposals are concerned Griffiths makes the following comments with regard to TfL’s modelling results:

“This gives 3 journey times, and the impact of CS9

2015 journey time,

2021 journey time*

2021 journey time with CS9 scheme

Impact of CS9 scheme on 2021 scenario

*Including future growth, committed schemes and consulted scheme at Hammersmith ie including the gyratory scheme

The figures it gives for the effect of CS9 is the difference between the last two times. That is the difference CS9 makes assuming the gyratory scheme is already in place. What one really needs to know is the difference between the first and the third set of times, the effect of the gyratory plus CS9

Hammersmith Bridge Rd to Shepherds Bush Rd          PM traffic

2015 journey time                                                    2-3 min

2021 journey time* [inc gyratory ]                          4-5 min

2021 journey time  [inc gyratory + CS9]              5-6 min

Impact of CS9 scheme on 2021 scenario           1-2 min

But the impact of [gyratory + CS9] on 2015  3-4 min say

Let us take the average 2015 journey time as      2.5 min

And the average 2021 journey time [+gyratory + CS9]    5.5 min.

The ratio of the two is 5.5/2.5 = 2.2, that is an 120% increase in the journey time across the gyratory.

This will have a massive effect on the queues on Castelnau and the Great West Rd.

A surprising observation from this CS9 PM Traffic chart is the time it takes to get from Holland Rd to Goldhawk Rd. This is 12 – 14 minutes in 2015, in 2021 with gyratory, and in 2021 with gyratory and CS9. I am surprised that it is so low, and that the 40% longer queuing time that we saw above is not reflected in the future.”

The full version is here.

London Assembly member Tony Devenish is asking Transport for London for a response.

One thought on “TfL urged to be admit the full extent of traffic delays that CS9 would cause

  1. Longer journey times were self evident from the beginning. If you have extra traffic lights for cycles only across the gyratory where they don’t exist currently longer waits for cars and pedestrians are guaranteed by this scheme. This scheme would snarl up most of the approaches to Hammersmith permanently. There must be a better route along the south of the gyratory, from the great west road, under the underpass, alongside the church in the car park, and then alongside the Novotel to Butterwick. It also reveals how the zealots of TFL refuse to see sense. We can see through these proposals. We know them for the fraud that they are.

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