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.
“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.