Mutton Lane - Darkes Lane Junction Proposal
Author: Tom Shirley.  Date: 25th June 2003

Executive Summary

This proposal by Tom Shirley makes various suggestions in relation to the modification of the Mutton Lane / Darkes Lane junction.  They are made by an amateur who does not have all relevant guidelines or junction information to hand.  Some of the suggestions may not be practical, legal or very sensible.  Please do not reject all suggestions just on the basis, that one or two are nonsense or you do not agree with.  All the suggestions can in general each be considered on its own merits.

The proposal makes the following improvements over the current junction.

The suggestions are summarised here with the author's detailed argument below.

1.  Plan of proposal.
The author has generated a plan, with modifications done by hand.  Not very professional, but hopefully clarifies the suggestions that follow. 

2.  Retain pedestrian refuges on each link.
The pedestrian refuges proposed are all 2m in depth, with a crossing width of 2.8m.

3. Mutton Lane West is increased to 2 lanes Eastbound
This is the same as the Mouchel proposal, except more space is taken from pavements to allow the refuge.

4. Echelon Parking loses some pavement on Darkes Lane west.
1.2m of pavement is lost to allow the Darkes Lane width to be increased without loss of parking on Darkes Lane west.

5. Footway Crossovers Introduced.
Four footway crossovers are proposed over side roads/drives to improve the pedestrian environment.

6. Traffic signal Phases.
Consideration should be given to a Baker St only phase, the phasing should assume in favour of the pedestrian, and consideration given to a green left filter from Mutton Lane west into Darkes Lane.

7. Traffic Signals not linked to Tesco lights
The author argues that linking to the Tesco lights will bear little, if any benefit.

8. Flat-topped crossing on Darkes Lane leg
This would be slightly raised and of different surface as a traffic calming measure at the entrance to the Darkes Lane shopping centre.

9. Changes consistent with Town Centre Action Plan 
Where possible, any changes in the road scheme should be consistent with the Town Centre Action Plan.

10. Minimise Pedestrian Guard Railing 
The natural inclination is that we should add as much pedestrian guard railing as money can afford, but there is little or no evidence this improves pedestrian safety.

11. Bus Stops
Perhaps the most controversial, but could we include 1 or 2 bus stops for buses coming from the station direction where the gap between stops is large.

 

The Detail

2.  Retain pedestrian refuges on each link.

Mouchel's argument for refuge removal.
This has been the most discussed issue about the junction.  It is clear that there was popular support for them at the 2 meetings.  Mouchel's  technical note dated 5/6/03 arguing for not retaining them maintains that the road is not wide enough to have pedestrian refuges.  But the author believes that this is based on a misunderstanding of the document "Providing for Journeys on Foot".  This document is supposed to be pro-walking, it therefore seems incredible if it argues that pedestrian refuges should not be considered.  The author suggests that when this document is talking about staggered crossings, it means that the crossing is staggered by virtue of the pedestrian needing 2 signal phases to cross the complete road.  That is why the document requires a staggered crossing to be installed on very wide crossings. On very wide crossings the time taken for a pedestrian to cross the complete road in one phase would be too much of a delay to the traffic in both directions. So, a pedestrian, to cross the complete road on a staggered crossing, would need to wait at the central refuge for a green man on a different phase of lights.  This is not the type of crossing, existing, or required for the Mutton Lane/Darkes Lane junction.  

On this subject, and in support of their argument, Mouchel engineers quote from "Providing for Journeys on Foot": "Pedestrians, who will be delayed in the centre of the carriageway, do not like staggered or divided crossing facilities".  I suggest that if the engineers think that what we have now is a "staggered or divided crossing facility", then this statement in "Providing for Journeys on Foot" is wrong.  We can quite easily test it by asking pedestrians who now use the junction whether they like the refuges or not.  

The author plans to tackle the IHT on this subject, as the same argument may be used to remove pedestrian refuges from not only the Tesco's, High St and Causeway junctions in Potters Bar, but presumably similar junctions across the county and country. 

Current Pedestrian Behaviour
The author did a survey of pedestrians between 08.00 and 08.30 (Wed 18/6/03).  In that time 166 pedestrians crossed the junction. 31 (19%) crossed all or part of the road during a green man phase.  Given that every 120 second cycle includes a 20 second (17%) pedestrian phase, then nearly every pedestrian that crossed on the green man, did so because it happened to be on when they needed to cross.  As every cycle also include a pedestrian phase, it is also clear that many pedestrians pressed the button, but did not wait for the green man.

The author suspects that later in the day, as less able pedestrians hit the street, more of them will wait for the green man.  So don't remove the green man!

So most pedestrians think it is an acceptable risk to cross the junction without the green man.  The author suspects they would be very unhappy to lose the refuges.  If the refuges go, some of them may wait for the green man, adding about 50 seconds to their average crossing time (not exactly pedestrian friendly) and some will still cross, and quite frequently they'll wait in the middle of the road.  This cannot be good for pedestrian safety. Not only does the refuge act as a refuge while traffic is passing, it is also a very clear indication, that you change from looking right, to looking left.

If we are still not convinced that we should retain the refuges, I suggest we consult with "Living Streets", formerly know as The Pedestrian Association.

How does this proposal facilitate the retention of refuges

Mutton Lane West.
A 2m refuge is achieved by taking more of the pavement on the North Side than just that required for making for 2 lanes Eastbound.  The current arrangement has 3.65m width westbound, 1.2m refuge and 3.8m eastbound. The Mouchel proposal (13/5/03) widens the road to 11m. This proposal needs 12m; 4m westbound, 6m eastbound, and 2m for the refuge.  It is not clear whether services under the pavement will make this extra 1m extremely expensive.  If this is the case,  and we need to restrict ourselves to the 11m width in the Mouchel proposal, then there are a number of options.  For example:  Westbound 3.65m as currently, refuge 1.35m (0.15m more than currently), eastbound 6m.

Darkes Lane
A 2m refuge is achieved by taking the same width of pavement on the East Side as in Mouchel's (13/5/03) proposal.  But unlike the Mouchel proposal, it does not change the pavement line on the west side. This allows a 4m lane Northbound, 2m of refuge, and 6m (3m per lane) Southbound

Mutton Lane East
A 2m refuge is achieved by widening the existing 1.55m refuge by 0.45m on its South side, and moving the South kerb line by the same amount.. This allows a 3.85m lane Eastbound (unchanged) , 2m of refuge, and 6m (3m per lane) Westbound.

Baker Street
A 2m refuge is achieved by taking the existing 1.2m refuge and increasing it by 0.8m on its west side without moving either pavement's kerb line. This leaves a 6.30m lane southbound (unchanged), 2m of refuge, and 6.2m (3.1m per lane) northbound (currently 7m).

This proposal increases the existing crossing's 2m and 2.8m widths to 2.8m on all legs.

This proposal leaves 3 refuges nearly all in their original position.  This means that the kerb line at the crossing is somewhat on the diagonal.  This may be considered undesirable, but acceptable in that this arrangement is much closer to the pedestrian's desire line.  None of the crossings will be quite so diagonal as some of those on the high street junction installed 2 years ago.  If it really is not acceptable, then they can be moved away from the junction, but this will impact parking and make the stop line closer to the bus stops.  The Mutton Lane west crossing is made considerably closer to the junction than currently to bring it closer to the pedestrian desire line, and take advantage of the deeper pavement on the Southside nearer the junction.

It may also be required to move the refuges away from the junction to improve the turning for buses and lorries.

3. Mutton Lane West is increased to 2 lanes Eastbound

This is the same as the Mouchel proposal, except more space is taken from pavements to allow the refuge. See section 2 above.  It is key to improving peak hour traffic flow.

4. Echelon Parking loses some pavement on Darkes Lane west.

If the plans from Mouchel are accurate, there is about 3m of public pavement on the west side and only 1.8 on the east side.  Given that none of the shops use all their own pavement, most none at all, it is proposed that 1.2m of the public pavement is used to move the echelon parking 1.2m to the west to allow the Darkes Lane width to be increased without loss of parking on Darkes Lane East.  This arrangement will give 4m of echelon parking, 3.5m northbound, 6m southbound and 2.1m east side parking.  This gain of 1.2m to the carriageway width will remove the existing infrequent congestion when 2 or 3 buses/lorries try to pass.  The plan incorporates a footway build-out at the North end of the echelon area to provide better sheltered parking.  This extreme parking slot would be extremely useful for disabled drivers, as the extension provides a convenient place to open the car door wide, and take as much time as possible without obstructing pedestrians on the main pavement, or obstructing traffic flow as happens in a parallel parking scenario. I would suggest that the other end of the parking is also used for disabled parking - perhaps more useful where it is the passenger that is disabled.  The only objection I can see to this proposal is if there isn't now 3m of public pavement, or where there are services under the pavement that really cannot take a weight of parked cars or lorries.  There are no inspection covers in the area effected.

5. Footway Crossovers Introduced.

Four footway crossovers are proposed  to improve the pedestrian environment. They are continuations of a footway across the mouth of a side road.  The road is raised at the crossing point, and uses a similar surface to that on the adjacent footway.  These crossovers allow vehicles to cross, but giving way to pedestrians.  The side roads proposed are the emergency entrance to Potters Court, The Close, and the two crossing points to the pavement outside Manor Court Flats (the pavement with the bus stop).  Perhaps even the entrance to Wyllyotts Place should get the same treatment.

6. Traffic signal Phases.

Baker St only phase
Consideration should be given to Baker St only phase.  There have been many complaints that turning right from Baker St is difficult and dangerous.  If it is not possible to have a green filter, then Baker Street should have its own phase.  This would also mean that Darkes Lane would also have its own phase.  This needs to be modelled.  Even if it reduces traffic flow, it should still be considered as a safety measure.

Phasing in favour of pedestrians
The phasing should assume in favour of the pedestrian whereby when a pedestrian presses the button, the lights go to pedestrian phase at the next possible break between traffic phases provided that at least a complete cycle has passed since the last pedestrian phase.  Clearly, it should then ago a complete cycle again before the next pedestrian phase (if requested).

Green left filter from Mutton Lane west
Consideration should be give to green left filter from Mutton Lane west into Darkes Lane while Darkes Lane southbound has a green right turn.  This would ease the congestion as so much traffic turns left into Darkes Lane, and often moves slowly due to echelon parking movements and other activities associated with a town centre.  This could be a problem to the right hand lane of Mutton Lane west as it would now carry straight on traffic as well as the very occasional right turner.  But it seems worth trying/modelling.

7. Traffic Signals not linked to Tesco lights

The author argues that linking to the Tesco lights will bear little, if any benefit.  According to IHT document "Transport in the Urban Environment", "adjacent signal-controlled junctions should be considered for co-ordination where travel times are less than 20-30 seconds normally, or 60 seconds in particularly free-flowing conditions".  Given that the Tesco lights are almost exactly 1km away, and therefore 75 seconds at 30mph, their application is right on the extremes of usefulness - even in free flowing conditions. Presumably there is some monetary cost in co-ordination.  It seems difficult to imagine that given the requirement to align cycle periods for this arrangement, there will not be some compromise at each junction for its own ability to change phasing to meet its own local demand.  The two junctions are quite different.  

8. Flat-topped crossing on Darkes Lane leg

This would be slightly raised and of different surface.  It would act as a traffic calming measure and reinforce the point to drivers that they are entering a shopping centre.  Not quite as extreme as that provided in Shenley Road, Borehamewood, but a similar purpose.  Surface finishes that significantly increase road noise should be avoided.

9. Changes consistent with Town Centre Action Plan 

Where possible, we should incorporate changes in the whole scheme that are consistent with the Town Centre Action Plan.  So we should include consistent designs in litter bins, seating, new lighting etc.  Additional signage should kept to a minimum, and use made of necessary street furniture such as lamp standards and bollards for the display of parking restrictions, directions etc.  Direction signage should be of a consistent design.

10. Minimise Pedestrian Guard Railing 

The natural inclination is that we should add as much pedestrian guard railing as money can afford, but there is little or no evidence this improves pedestrian safety.  To quote the report of the House of Commons Transport Select Committee under Gwyneth Dunwoody:

"There seems to be no available statistical evidence about crashes to support the general use of these railings or (staggered) crossings. In some instances they increase the likelihood of injury. The evidence which we received indicated that danger reduction is probably a more effective way of reducing pedestrian casualties."  and "Danger reduction, using speed management, would also allow miles of guard railings and many staggered, cattle pen crossings to be scrapped. These grotesque items both inconvenience pedestrians and disfigure our cities."

Full text:  http://www.parliament.the-stationery-office.co.uk/pa/cm200001/cmselect/cmenvtra/167/16702.htm

The case of Kensington High Street where guard railing was removed is interesting in this respect.  See press release.

11. Additional Bus Stops

We talk a lot about improving public transport, perhaps we can actually do it here by incorporating 1 or 2 extra bus stops for buses coming from the railway station  where the gap between stops is large.  All buses (without exception?) now go through, or terminate at the railway station.

The distance from the railway station to the next bus stop eastbound at Tescos is 1.2km.  Given that IHT document "Transport in the Urban Environment" calls for typical bus stop frequency between 2 and 3 stops/km, we could do with another stop.  The best place for passengers would be just to the East of the junction on Mutton Lane and is shown on the plan.  This would benefit anyone that lives South or west - a large catchment area, plus shoppers in The Broadway.  It would save the walk to the station, and avoid them having to wait at the station, something that many people find intimidating at the moment.  A bus stop would mean loss of some parking, or perhaps interrupt traffic flow. Interrupting traffic flow is becoming more acceptable given the encouragement given to public transport.  So what if occasionally a dozen cars have to wait 10 seconds or so while a bus picks up passengers saving them each a couple of minutes walk to the station. 

The suggestion of this bus stop has been passed to the Passenger Transport Unit at County Hall (reference number 2592282).

What arguments will there be against a bus stop here:

a)  There is another bus stop just the other side of the junction.  The Passenger Transport Unit queried this.  But with the present routing, no buses go straight from Mutton Lane East to Mutton Lane West.  All of them go to the station.  The 298 is the only bus that would go to both these bus stops, but with a diversion to the station between. 

b)  The buses pulling in and out of the stop would cause a safety issue.  Given that any bus pulling into the stop would have just come round the corner from Darkes Lane, it would be travelling slowly anyway, as would any vehicle following it.  On seeing a waiting passenger it would just gently pull in, the vehicles behind travelling slow enough to take necessary action to prevent a risk.  When the bus comes to pull away again, it can take advantage of the natural breaks in the traffic caused by the traffic lights.

c)  The bus stop lay-by as shown on the plan does go straight over a large inspection cover.  This will need to be strengthened.  Possibly not worthwhile to just provide a car parking bay, but perhaps worthwhile if it facilitates a bus stop.

It should also be noted that the bus stops shown on the plan are 20m long, whereas a typical bus is 10m long.

Preferably a bus shelter would be provided as it would be almost exclusively a pick-up bus stop. 

The distance from station to the next bus stop westbound at Laurel Avenue is 0.8km.  And given that Laurel Avenue is closer to most of the same catchment area perhaps this is not so critical.  But still it should be considered.  The options are to have a stop where it is bound to delay vehicles or use the turning for Weston Close as a bus pull-in.

On the subject of bus stops.  The existing bus stop on the South side of Mutton Lane is almost exclusively a set-down point - as in most cases the next stop is the station where the bus terminates.  Given that, a bus shelter is not essential here.  But we should still do something about the existing ugly monstrosity.

End of Document

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