north west preston aimsun microsimulation...

North West Preston Aimsun Microsimulat ion Model Additional Modelling Report – July 2017 LCC 2034 Do Minimum scenario

Additional Modelling Report LCC Do Minimum Scenario

Additional Modelling Report

Contents

1. Introduction ......................................................................................................... 2

1.1 Overview................................................................................................... 2

1.2 Initial Microsimulation Model ..................................................................... 2 1.3 Limitations of the initial model (Fore 2034 Do Minimum scenario) ........... 3

2. Model Development ............................................................................................ 5

2.1 Purpose of the additional modelling .......................................................... 5

2.2 Aimsun Version ........................................................................................ 5 2.3 Extent of the model ................................................................................... 5

2.4 Modelled Time Periods ............................................................................. 8 2.5 Vehicle Types ........................................................................................... 8

2.6 Traffic Signal Coding ................................................................................ 8 2.7 Public Transport ....................................................................................... 8

2.8 Traffic Demand ......................................................................................... 9 2.8.1 Observed Traffic Data ................................................................. 9

2.8.2 Matrix Development .................................................................... 9 2.9 Model Verification ..................................................................................... 9

2.10 Model Calibration .................................................................................... 9 2.11 Model Validation ..................................................................................... 9

3. Network coding changes .................................................................................. 10

3.1 Network Development ............................................................................ 10

3.2 Matrix Development ................................................................................ 11 3.2.1 Sites in North West Preston ...................................................... 11

3.2.2 Zone Splitting ............................................................................ 13

4. Results – Local Impacts of the Scheme .......................................................... 18

4.1 Selection of Model Output Data .............................................................. 18 4.2 Model Outputs ........................................................................................ 19

4.2.1 2034 Do Minimum - Simulated Delay Time ............................... 19 4.2.2 2034 Do Minimum – Simulated Traffic Flow ............................. 20

4.2.3 2034 Do Something - Simulated Delay Time ............................ 22 4.2.4 2034 Do Something - Simulated Traffic Flow ............................ 22

5. Summary and Conclusion ................................................................................ 34

5.1 Introduction ............................................................................................. 34 5.2 Future Year Modelling ............................................................................ 34

Appendix A Model Output Plots ...................................................................... 35

NW Preston Aimsun Microsimulation Model – Additional Modelling Report

• 2 •

1. Introduction

1.1 Overview

This report supplements the North West Preston Aimsun Microsimulation Model

Modelling Report (October 2016) and documents additional microsimulation

modelling undertaken by Lancashire County Council (LCC).

Additional modelling utilises the initial model developed by Fore Consulting Limited

(Fore), covering the same geographical extents, in the development of a new 2034

Do Minimum scenario with an increased level of detail demonstrating the impacts on

the network without the proposed Preston West Distributor (PWD) and East West

Link Road (EWLR) scheme. The initial base network and 2034 Do Something

scenarios are unchanged.

This report is therefore to be viewed in conjunction with the initial Modelling Report

document (October 2016) which sets out the development, calibration and validation

of the microsimulation model.

1.2 Initial Microsimulation Model

Jacobs were appointed by LCC to develop an Aimsun microsimulation model

covering an area of North West Preston, in conjunction with Fore. The full North

West Preston Masterplan along with the proposed Preston West Distributor (PWD)

and East West Link Road (EWLR) were considered in the study.

The model included 3 scenarios; the base network (current situation), 2034 Do

Minimum (forecast without the scheme), and 2034 Do Something (forecast with the

scheme). Development, verification, calibration and validation of the microsimulation

model is set out in the Modelling Report document (October 2016).


• 3 •

1.3 Limitations of the initial model (Fore 2034 Do Minimum

scenario)

The proposals for the North West Preston Masterplan have been accounted for in

both the 2034 Do Minimum (DM) and 2034 Do Something (DS) scenarios to test the

change / impact of including the EWLR scheme.

The 2034 Do Minimum scenario developed by Fore (figure 1) in the initial

microsimulation model is however limited by its development in accordance with the

Central Lancashire Traffic Model (CLTM) 2034 Do Minimum network.

The following limitations are identified in the Fore 2034 DM scenario and resolved in

the development of the LCC 2034 DM scenario;

Limits of the Network Layout

In replicating the network layout from the CLTM in the development of a 2034 Do

Minimum microsimulation scenario, a notable level of detail has been omitted from

the Fore 2034 DM scenario. New internal roads associated with planned

development sites are not included limiting vehicle routing options.

Limits of the Development Site Zone Splitting

CLTM zones have been split to provide an increased number of zones in the Aimsun

Model however zone splitting is not extensive enough to allocate each development

site in NW Preston its own zone. This limits the level of detailed analysis that is

possible in considering the impacts of each development site.

Limits of the Zone Loading Points

Development site zone loading (the point at which vehicles enter and exit the

network) does not consider the possibility of new access points onto the existing

network being created in the absence of the EWLR.

In the Fore 2034 DM scenario vehicles associated with new development sites are

loaded onto the network at loading points associated with existing properties (i.e.

Melbourne Estate) as per the base network. Whilst ensuring that all vehicle demand

associated with proposed developments is included on the network, the distribution

of this traffic is restricted because vehicles are loaded onto the network across a

small number of loading points.

Traffic associated with various development sites should be distributed on to the

network via multiple access points. New hypothetical access points associated with

each individual development sites should therefore be included.


• 4 •

Figure 1: Geographical extent of the Fore 2034 Do Minimum scenrio network including location of vehicle loading zones (zone ID's numbered)


• 5 •

2. Model Development

2.1 Purpose of the additional modelling

The additional modelling (LCC 2034 Do Minimum scenario) is intended for use in

further testing the impacts of the proposed North West Preston Masterplan on the

surrounding highway network. The microsimulation model has been developed to

identify the implications of delivering the proposed PWD and EWLR on the

masterplan area. The addition of a 2034 Do Minimum network with an increased

level of detail and functionality, specifically in relation to the distribution of traffic from

proposed development sites and the routing options generated by access roads

associated with the proposed development sites, enables an enhanced level of

micro-simulation analysis.

2.2 Aimsun Version

The additional modelling has been developed in Aimsun version 8.1.3 (R40314 x64).

2.3 Extent of the model

The scope and extent of the Aimsun model is unchanged from that reported in the

Modelling Report (October 2016).

The model covers an area on the north-western outskirts of Preston which includes

Cottam, Lower Bartle, and Higher Bartle.

The model extends as far as the M55 overpass to the north, and up to and including

the B6241 / Tanterton Hall Road / B5411 roundabout to the south. In a west-east

direction the model extends from Sidgreaves Lane to the B6241 Lightfoot Lane.

The following access junctions (some of which are hypothetical) have been added to

the LCC 2034 DM Scenario:

Sidgreaves Lane / development site north of Hoyles Lane access;

Hoyles Lane / development site north of Hoyles Lane access;

Sandy Lane / Maxy House Farm access;

Lea Lane / development site east of Lea Lane access;

Bartle Lane / development site south of Bartle Lane access;

Bartle Lane / development site west of Sandy Lane access;

Sandy Lane / development site west of Sandy Lane access;

Sandy Lane / development site east of Sandy Lane access (north);


• 6 •

Sandy Lane / development site east of Sandy Lane access (south);

Sandy Lane / Haydock Grange access (north);

Sandy Lane / Haydock Grange access (south);

4 arm roundabout on Tabley Lane providing access to Haydock Grange site

and to land north of Lightfoot Lane;

Lightfoot Lane / development site east of Tabley Lane access; and,

3 arm roundabout on B6241 providing access to land between Lightfoot Lane

and Sandyforth Lane.

The following through routes have been added to the LCC 2034 DM Scenario:

Sidgreaves Lane to Sandy Lane with a connection to Hoyles Lane (through

development sites north of Hoyles Lane)

Sandy Lane to Tabley Lane (through Haydock Grange site)

Tabley Lane to Lightfoot Lane (through pocket of land east of Tabley Lane)

The geographical extent of the LCC 2034 DM scenario is shown in Figure 2.


• 7 •

Figure 2: Geographical extent of the LCC 2034 Do Minimum scenario network


• 8 •

2.4 Modelled Time Periods

The LCC 2034 Do Minimum scenario has been developed in accordance with the

initial model and is representative of typical conditions during the following time

periods:

AM peak period: 08:00 to 09:00

PM peak period: 17:00 to 18:00

These periods were chosen as they capture peak traffic flows on the highway

network, in accordance with the Central Lancashire Highways and Traffic Model

(CLTM).

In addition, a fifteen minute warm-up period has been used to generate the initial

starting point for the model.

2.5 Vehicle Types

The model considers the following vehicle types:

Cars – comprising private cars and taxis;

Light goods vehicles (LGVs) – with a gross vehicle weight of less than 3.5t;

Heavy goods vehicles (HGVs) – with a gross vehicle weight greater than 3.5t;

and,

Buses – comprising all public service buses.

2.6 Traffic Signal Coding

Unchanged from the Fore model. See Modelling Report (October 2016)

2.7 Public Transport



• 9 •

2.8 Traffic Demand

2.8.1 Observed Traffic Data


2.8.2 Matrix Development

Base and 2034 Do Something matrices are unchanged from the Fore model. See

Modelling Report (October 2016)

A new 2034 Do Minimum matrix was generated as is outlined in section 3.2 of this

report.

2.9 Model Verification

Simulated model unchanged from the Fore model. See Modelling Report (October 2016)

2.10 Model Calibration

The modelling parameters were unchanged from those used in the initial model built

by Fore. Stochastic dynamic traffic assignment (DTA) has been used in the

additional modelling, as it was in the Fore model, to determine the paths that

vehicles will take between a given origin and destination from a set of alternative

routes as outlined in the Modelling Report (October 2016). The Logit model is

therefore applied to determine route choice in running the LCC 2034 DM scenario.

A supplementary run of the LCC 2034 DM scenario was performed with route choice

fixed using travel times calculated under free-flow conditions to provide further

analysis and demonstrate the influence of delay time on outputs associated with the

Logic route choice model.

2.11 Model Validation

Simulated model unchanged from the Fore model. Validation outlined in Modelling

Report (October 2016)


• 10 •

3. Network coding changes

3.1 Network Development

The LCC 2034 Do Minimum network layout has been manually constructed using

Aimsun, utilising the network layout developed by Fore in the initial microsimulation

model scenarios as a foundation from which to develop the LCC 2034 DM network.

Links associated with the PWD and EWLR scheme were removed and changes to

the existing network such as severance of Sidgreaves Lane were reinstated to

generate network layout that was representative of a without scheme situation that

includes all development site residential roads.

As outlined in section 1.3, one limitation of the Fore 2034 DM network is the zone

loading points of proposed development sites in the absence of the EWLR. To

alleviate this limitation, hypothetical alternative access arrangements (as outlined in

section 2.3) were determined to provide specific loading points on to the network at

individual development sites.

Access junctions on Lea Lane, Bartle Lane, Sandy Lane (south of Bartle Lane from

the east), and adjoining the Nog Tow roundabout to the east of Tabley Lane were

generated to load vehicles onto the network from development sites that are

accessed by the EWLR in the 2034 DS scenario.


• 11 •

3.2 Matrix Development

Existing matrices created by Fore were used to generate a new set of matrices in the

LCC 2034 DM scenario to replicate the distribution of trip from the proposed

development sites in North West Preston. Key to this was the splitting of zones

associated with development sites in the North West Preston area to produce an

increased number of zones enabling trips associated with each development site to

be loaded on to the network at multiple loading points.

3.2.1 Sites in North West Preston

North West Preston masterplan outlines the land ownership parcels across the area

each representing a site identified for development or privately owned. Land parcels

identified for development are coded in to the model as zones, generating future

traffic growth. 14 individual sites in North West Preston were identified based on

planned and consented development boundaries and labelled A to N as shown in

figure 3. Sites A, B, G, I, M and N (outlined in black) were consented at the time of

the model development.

The number of dwellings associated with each development site, determined by

planning applications where consented or approximation based on the size of the

site, is shown in table 1. Through the zone splitting exercise some sites were

rebalanced to more accurately determine the number of dwelling modelled for each

site based on the total number of dwellings in the model.

Traffic generated by site J is also inclusive of traffic associated with community

infrastructure in North West Preston.


• 12 •

Figure 3: North West Preston Development Sites


• 13 •

3.2.2 Zone Splitting

Matrices included in the Fore 2034 DS scenario were used in the zone splitting

exercise given the validity of the development site zone allocations in the DS model.

Matrix redistribution associated with the removal of the PWD origin-destination points

was applied to each of the matrices prior to splitting exercise.

The Fore 2034 DS network included 7 zones associated with developments in North

West Preston generating development traffic. Some of these zones can be match

directly with an individual development site, whilst others generate trips associated

with multiple sites. As shown in figure 4 the zones are numbered as follows;

1659503549 (inclusive of site A)

1659503550 (inclusive of site B)

1659503551 (inclusive of sites C, D, E, F, G, H)

1659503552 (inclusive of site I)

1659503879 (inclusive of site J + community infrastructure)

1659503648 (inclusive of sites K, L, M)

1659503707 (inclusive of site N)

Zone splitting was therefore applied to zones 1659503551 and 1659503648 as

shown in table 1 to generate new matrices for the LCC 2034 DM network (figure 5)

including the 14 sites identified in North West Preston.

A percentage split for each zone in the LCC model was determined based on the

actual and approximate number of dwellings at each site. These percentages were

then applied to the matrices to generate trips for each zone in line with the total

amount of development traffic in the model. Applying this percentage to the total

number of dwellings in the model for the Fore Zone enabled the number of dwelling

in the LCC model for each zone to be identified and ensured no trips were lost from

the model. The number of dwellings in the LCC model was checked against

information available for consented sites and rebalancing was applied to improve the

accuracy of zone loading.

Zone 1659503707 (site N) did not require splitting however it was noted that the Fore

model accounted for 401 dwellings whilst the site had been consented for 371

dwellings. Zone N was therefore adjusted accordingly to remove the trips associated

with the extra 30 dwellings resulting in a loss of 7.5% of trips from zone N.


• 14 •

Splitting example:

It was approximated that zone C contained 350 dwellings representing 19.13% of the

sum of all dwellings (actual and approximated) in zones C, D, E, F, G, H;

The 19.13% split was then applied to cells in the matrices associated with the Fore

zone (1659503551) to generate trips for zone C.

Based on the number of dwellings in the Fore model, as per the matrices, the trips

generated by zone C was calculated to be the equivalent of 280 dwellings.

Rebalancing example:

As a consented site, zone G was known to contain 230 dwellings. A split of 12.57%

represented 184 dwellings so a rebalancing was applied to increase zone G to 230

dwellings in turn resulting in a 15.70% split in the matrices to generate the trips

associated with zone G. The percentage split applied to the matrices for Zone H was

consequently reduced from 10.93% to 7.80%.

This rebalancing ensured that all trips associated with consented sites were

modelled with the highest level of accuracy.


• 15 •

Table 1: North West Preston Development Site Zone Splitting

Fore Zone Number

Site Ref / LCC Zone Site Description

No dwellings in Fore Model

No dwellings actual/approx

Consented (Y/N)

Sum of actual/approx

Zone split %age

actual/approx

Rebalance based on

consented Dwellings in new model

1659503549 A Land North of Hoyle's Lane 350 350 Y 350 100.00% 350

1659503550 B Maxy House Farm 350 350 Y 350 100.00% 350

1659503551

C

Remainder west of Sandy Lane

1465

350 N

1830

19.13% 280

D 350 N 19.13% 280

E 350 N 19.13% 280

F 350 N 19.13% 280

G 230 Y 12.57% 15.70% 230

H 200 N 10.93% 7.80% 114

1659503552 I Haydock Grange 450 450 Y 450 100.00% 450

1659503879 J Between Sandy Lane &

Tabley Lane 264 264 N 264 100.00% 264

1659503648

K East of Tabley Lane

(Redrow) 522

175 N

700

25.00% 17.00% 89

L 195 N 27.86% 19.80% 103

M 330 Y 47.14% 63.20% 330

1659503707 N East of Tabley Lane 401 371 Y 371 108.09% 92.52% 371

TOTAL 3802 4315 3772


• 16 •

Figure 4: Fore 2034 Do Something scenario network including location of vehicle loading zones (zone ID's numbered)


• 17 •

Figure 5: LCC 2034 Do Minimum scenario network including location of vehicle loading zones assicated with development sites (labelled A-N)


• 18 •

4. Results – Local Impacts of the Scheme

The LCC 2034 Do Minimum scenario has been run and compared to the Fore 2034

Do Something scenario within Aimsun.

Appendix A presents a series of plots showing model-wide outputs from these

scenarios.

Screenshots from the network plots of the LCC 2034 DM and Fore 2034 DS

scenarios focusing on the Tabley Lane / Sandy Lane area have also been produced.

These are presented in Figure 6 to Figure 9 for the AM peak and in Figure 10 to

Figure 13 for the PM peak.

Supplementary screenshots showing the LCC 2034 DM network under free-flow

conditions in the Tabley Lane / Sandy Lane area are presented in Figure 14 for the

AM peak and Figure 15 for the PM peak. The free-flow network is void of all delay,

therefore route choice is not influenced by capacity constraints at junctions - this is a

hypothetical situation that would require extensive and largely undeliverable network

alterations to achieve.

4.1 Selection of Model Output Data

Peak period traffic flow data is commonly used in network analysis and is referred to

in the October 2016 Modelling Report. Traffic flows on links can however be

influenced by the level of delay associated with a particular link, viewing forecast

flows in isolation can therefore fail to demonstrate network performance, particularly

where parts of the network are congested.

Along a link that experiences delay (stationary queuing traffic), link flows across the

modelled time period are lowered as a result of free-flow conditions being

compromised. Along a route consisting of multiple links, link delay creates the

impression of varying traffic flows along the route with lower flows along links with

higher delay.

Within the modelled period, delay is initially applied to the link that coincides with its

point of origin (typically at a junction). As the resultant traffic queue builds, vehicles

flowing along links approaching the queue continue to move freely until the length of

the queue extends to include additional links in the model. The delay time across

multiple links is combined to calculate the sum of total cumulative delay along a

route. A congested route therefore contains lower traffic flows. These flows are

constrained by the presence of queuing traffic – if viewing route flows only, these

'low traffic flows' can create the impression of a positive output from the model. The

impression of 'lost' vehicles can also be created where flows along a given road vary

as a result of delay and the resulting queuing traffic.

Based on this link flow information should also be viewed alongside link delay time

information in order to fully understand the modelled network performance.


• 19 •

4.2 Model Outputs

Comparison of traffic flows in the LCC 2034 DM scenario with the Fore 2034 DS

scenario does not fully demonstrate the performance of the network in a Do

Minimum situation – particularly along Tabley Lane, Sandy Lane and the residential

roads associated with the Haydock Grange site – as vehicle routing is influenced by

the associated delay time along each link.

4.2.1 2034 Do Minimum - Simulated Delay Time

Across both peak periods in the LCC 2034 DM scenario the network in the North

West Preston areas experiences extremely high levels of delay resulting in

congestion to the point of near gridlock.

Delays in the 2034 DM scenario stem from the Tom Benson Way / Tag Lane

roundabout, Tabley Lane / Hoyles signal controlled junction and the roundabout on

Tabley Lane at Nog Tow.

The movement of vehicles in the NW Preston Area is intrinsically tidal. AM trips are

typically journeys 'from home' therefore there is a greater movement in the general

south-east direction from routes such as Tabley Lane, Sandy Lane and Hoyles Lane

towards the Tom Benson Way / Tag Lane roundabout in the 2034 DM scenario.

Conversely PM trips are typically 'return to home' journeys therefore movements in

the general north-west direction pass through the Tom Benson Way / Tag Lane

roundabout before reaching routes such as Tabley Lane, Sandy Lane and Hoyles

Lane.

Over the AM peak period (figure 8) widespread delays occur across the network with

queuing traffic first forming along Tabley Lane southbound and Hoyles Lane

eastbound.

Tabley Lane southbound experiences cumulative delays between the Nog Tow

roundabout and Maxy Lane of 1,563 seconds (approx. 26 minutes). Further delays

extend further northwards along Tabley Lane representing queuing vehicles along

the full length of Tabley Lane. In seeking to avoid these delays vehicles re-route via

Maxy Lane to Sandy Lane.

As the AM peak period develops the length of the queue on Hoyles Lane extends to

Sandy Lane resulting in queueing vehicles along Sandy Lane. Vehicles re-routing

from Tabley Lane via Maxy Lane extenuate this queue. The cumulative delay time

along Hoyles Lane eastbound and Sandy Lane southbound between Tag Lane and

Bartle Lane is 1,485 seconds (approx. 24 minutes).

Further re-routing occurs through the residential estate roads associated with the

Haydock Grange development site. In turn these roads experience delay and severe


• 20 •

levels of congestion. With no further re-routing options available the network

approaches a state of gridlock as traffic continues to build over the AM peak period.

South of Hoyles Lane there are large delays on all northbound and westbound

approach arms on the Tom Benson Way / Tag Lane junction. Tag Lane northbound

experiences delays of 1101 seconds (approx. 18 minutes), and delays on Tom

Benson Way approaching the roundabout northbound and southbound are 381

seconds (approx. 6 minutes) and 411 seconds (approx. 7 minutes) respectively.

These delays constrain the respective northbound and westbound traffic flows on

Tabley Lane, Sandy Lane and Hoyles Lane.

In the PM peak (figure 12) the level of delay across the network is less severe

however queues on Tabley Lane southbound and Hoyles Lane eastbound form as

per the AM peak and result in a similar pattern of re-routing as the network

approaches a state of near gridlock. The cumulative delay time on Tabley Lane

southbound is 328 seconds (approx. 5 minutes) whilst Hoyles Lane eastbound

experiences delays of 340 seconds (approx. 5 minutes).

There are delays on Tag Lane northbound of 1129 seconds (approx. 18 minutes)

and on Tom Benson Way approaching the roundabout northbound and southbound

of 437 seconds (approx. 7 minutes) and 547 seconds (approx. 9 minutes)

respectively. These delays are slightly greater than those in the AM peak and have a

similar effect of constraining northbound and westbound traffic flows on Tabley Lane,

Sandy Lane and Hoyles Lane.

4.2.2 2034 Do Minimum – Simulated Traffic Flow

The existence of delay on certain links results in lower flows as traffic is unable to

'flow' given the presence of stationary queuing traffic. Delay at a junction also has

the potential to constrain the flow of traffic further along the journey path, particularly

where alternative routing is not possible or limited by the extents of the model,

resulting in lower flows. Conversely, other parts of the network experience higher

flows as traffic re-routes to avoid delays until a tipping point is reached where links

on which re-routing occurs are also delayed.

Figure 6 shows the southbound flow on Tabley Lane to be 77 vehicles in the AM

peak. Viewed in isolation this would suggest that there is a low level of demand

associated with southbound movements on Tabley Lane. Giving consideration to the

delay time (approx. 26 minutes) shown in figure 8 it becomes clear that these

seemingly low flows are a result of a heavily congested route along which traffic

flows are constrained by the severity of delay along each link and reflect the

presence of queueing traffic.

The principle of delay time influencing route choice is underlined when the LCC 2034

DM network is simulated under free-flow conditions (i.e. without the influence of


• 21 •

delay). Figure 14 shows the traffic flows in the AM peak in a 2034 DM network where

all delay has been removed – demonstrating that if the network was free of

congestion and queues did not form, Tabley Lane would experience traffic flows of

378 vehicles in the southbound direction.

Northbound on Tabley Lane, whilst there is no delay associated with the links

themselves, a simulated flow in the AM of 88 (figure 6) is influenced by delay times

at the Tom Benson Way / Tag Lane roundabout as northbound traffic flow is

constrained by congestion at a previous stage in the journey path. Figure 14 shows

northbound flows on Tabley Lane under free flow conditions to be 152. The same

applies to Hoyles Lane westbound.

The geographical extents of the model does not include the network west of Tom

Benson Way and south of Hoyles Lane (i.e. Merry Tree Lane, Cottam Way, Lea

Road) the inclusion of which would facilitate re-routing from south of the Tom

Benson Way / Tag Lane junction intensifying congestion along routes such as

Hoyles Lane.

Elsewhere under free-flow conditions in the AM peak there are lower flows on Sandy

Lane southbound and along the Haydock Grange residential estate roads eastbound

as re-routing does not occur. Eastbound flows on Hoyles Lane are higher as the

delay constraining the flows has been removed.

A similar pattern of flow occurs across the LCC 2034 DM scenario in the PM peak

period (figure 10) as queuing traffic associated with delay on Tabley Lane

southbound and Hoyles Lane eastbound results in re-routing along Sandy Lane via

Maxy Lane and through the Haydock Grange development site. High traffic flows

westbound on Maxy Lane in the PM are another example of how viewing simulated

flows in isolation does not fully explain the situation on the network.

A westbound flow on Maxy Lane of 240 vehicles in figure 10 is greater than the flow

on Tabley Lane southbound south of Maxy Lane. The delay time on Tabley Lane

southbound (approx. 5 minutes) results in re-routing via Maxy Lane becoming a

more attractive option. Under free flow conditions (figure 15) just 1 vehicles travels

westbound along Maxy Lane with the remaining vehicles reverting to Tabley Lane in

the absence of delay – resulting in a southbound flow along Tabley Lane, under free-

flow conditions, of 464 vehicles.

Delays on Tom Benson Way and Tag Lane at the roundabout junction, as per the

AM peak, constrain traffic flows on Tabley Lane northbound and Hoyles Lane

eastbound.


• 22 •

4.2.3 2034 Do Something - Simulated Delay Time

Delay time outputs from the simulated Do Something network have been generated

for both peak periods (figures 9 and 13).

Comparison of delay across the network in the DS to the delay time outputs from the

LCC 2034 DM (figures 8 and 12) is the most effective way to understand the impacts

of the scheme on the local network.

The introduction of the PWD and EWLR scheme completely removes all unintended

delay across the North West Preston network in both peak periods relieving

congestion.

Residual delays on the network (i.e. figure 9 shows 24 seconds of delay time on

Hoyles Lane at the junction with Tabley Lane) are those associated with signal

timing intergreen phases and do not result in queueing traffic beyond the intended

signal cycle time.

Across both peak periods along the main lines of Tabley Lane, Sandy Lane, Hoyles

Lane, Tag Lane, Tom Benson Way and residential estate roads through Haydock

Grange experience delay times of either zero or negligible interest.

The simulated delay time outputs demonstrate that through the removal of delay, the

PWD and EWLR scheme significantly improves the performance of the highway

network in North West Preston.

Additional connections to the existing network provided by the scheme in the 2034

DS scenario generate alternative route choice options, particularly for journeys

to/from Preston and the motorway network. Given the tidal nature of trips in the NW

Preston Area, these additional route choices widen the spread of vehicle movements

and lessen the weight of journeys south-east towards the Tom Benson Way / Tag

Lane roundabout in the AM and north-west through the roundabout in the PM.

4.2.4 2034 Do Something - Simulated Traffic Flow

Given the absence of delay from the network, simulated flows in the Do Something

scenario are representative of optimum route choice (i.e. flows are not influenced by

re-routing caused by congestion).

The introduction of the PWD and EWLR scheme provides alternative access

arrangements for development sites and additional connections to/from the strategic

highway network. Traffic flows in the DS scenario reflect the alternative distribution of

traffic resulting from the inclusion of the scheme, particularly on Sandy Lane and

Tabley Lane south of the EWLR.

Connection to the M55 Junction 2 provides a strategic alternative to Junction 1 and,

as such, attracts both development-associated and existing traffic that would have

otherwise travelled east. Additionally, the PWD which also provides a strategic link

towards south, in combination with the severance of Sidgreaves Lane and the


• 23 •

implementation of traffic calming measures, is likely to reduce traffic on Hoyle’s

Lane.

As already established, comparison of traffic flows in the DM (figures 6 & 10) and DS

(figures 7 & 11) does not provide suitable analysis due to the levels of delay on the

network in the Do Minimum scenario. Traffic flow increases on Tabley Lane and

associated decreases on Sandy Lane, Hoyles Lane, and through Haydock Grange

are largely a consequence of congestion relief.

Figures 14 and 15 showing the DM network under free-flow conditions (removal of all

delay) provide some level of comparison in terms of understanding the impact of the

scheme on unconstrained route choice. The introduction of the scheme results in

general reductions on Sandy Lane and Hoyles Lane, particularly west of Sandy

Lane, and slight increases on residential estate roads through Haydock Grange.

On Tabley Lane south of the EWLR, based on free-flow conditions in the DM

scenario, the scheme results in increases northbound and reductions southbound

across both peak periods; 2-way flows are largely unchanged. This demonstrates

that even if congestion in a Do Minimum scenario was eradicated (through the

delivery of unattainable network alterations), Tabley Lane would not suffer adverse

impacts in relation to traffic flow through the introduction of the scheme.

Traffic flows on Tabley Lane south of the EWLR in the Do Something scenario

across the AM peak period (figure 7) are 240 vehicles northbound and 324 vehicles

southbound. In the PM (figure 11) the simulated flows are 258 northbound and 318

southbound.

The forecast traffic flows on Tabley Lane in the Do Something scenario indicate that

the road is operating with spare vehicular capacity. As a B Road, Tabley Lane is

assumed to have a lane capacity of 800 vehicles per hour. In the instance with the

highest flow (northbound AM) there remains 59.5% space capacity.

Taking into consideration the geometry of Tabley Lane – which is in parts not typical

of a standard B Road – spare capacity under the parameters of a residential 30 mph

road (with an assumed lane capacity of 600 vehicles per hour) remains greater than

46% across both directions in both peak periods. This reaffirms the forecast traffic

flows on Tabley Lane to be of an acceptable level.


• 24 •

Figure 6: Tabley Lane / Sandy Lane Simulated Flow – LCC 2034 Do Minimum AM

Simulated flows shown in vehicles per hour


• 25 •

Figure 7: Tabley Lane / Sandy Lane Simulated Flow – Fore 2034 Do Something AM



• 26 •

Figure 8: Tabley Lane / Sandy Lane Simulated Delay Time – LCC 2034 Do Minimum AM

Delay time shown in seconds per link


• 27 •

Figure 9: Tabley Lane / Sandy Lane Simulated Delay Time – Fore 2034 Do Something AM



• 28 •

Figure 10: Tabley Lane / Sandy Lane Simulated Flow – LCC 2034 Do Minimum PM



• 29 •

Figure 11: Tabley Lane / Sandy Lane Simulated Flow – Fore 2034 Do Something PM



• 30 •

Figure 12: Tabley Lane / Sandy Lane Simulated Delay Time – LCC 2034 Do Minimum PM



• 31 •

Figure 13: Tabley Lane / Sandy Lane Simulated Delay Time – Fore 2034 Do Something PM



• 32 •

Figure 14: Tabley Lane / Sandy Lane Simulated Flow under Free Flow Conditions – LCC 2034

Do Minimum AM



• 33 •

Figure 15: Tabley Lane / Sandy Lane Simulated Flow under Free Flow Conditions – LCC 2034

Do Minimum PM



• 34 •

5. Summary and Conclusion

5.1 Introduction

Following the identification of limitations in the 2034 Do Minimum scenario within the

microsimulation model developed by Fore Consulting Limited (Fore), additional

modelling was undertaken by Lancashire County Council (LCC).

The additional modelling utilises the initial microsimulation model, covering the same

extents, in the development of a new 2034 Do Minimum scenario with an increased

level of detail. The initial base network and 2034 Do Something scenarios are

unchanged.

5.2 Future Year Modelling

During both peak periods in the LCC 2034 Do Minimum scenario the modelled

network experiences significant levels of delay that results in re-routing and

widespread congestion culminating in the network reaching a state of near gridlock.

Delays of up to 26 minutes result in lengthy traffic queues on Tabley Lane, Hoyles

Lane, Sandy Lane and through the Haydock Grange sites in addition to congestion

on all arms of the Tom Benson Way / Tag Lane roundabout.

The introduction of the PWD and EWLR scheme in the Fore 2034 Do Something

scenario results in the complete removal of all unintended delay across the North

West Preston network in both peak periods relieving congestion.

Through the relief of widespread delay in the North West Preston area, the scheme

can be said to have beneficial impact on the network.

Whist the additional connections to the strategic highway network, chiefly the M55

junction 2, results in an alternative distribution of traffic – particularly on Sandy Lane

and Tabley Lane south of the EWLR – simulated flows outputs demonstrate there to

be spare vehicular capacity remaining on each of these routes (excess of 46% spare

capacity on Tabley Lane).

The relief of all delay across the network and the existence of spare capacity on

existing roads, demonstrates the clear benefits of the schemes and its ability to

mitigate against the impacts associated with the delivery of development associated

with the North West Masterplan.


• 35 •

Appendix A Model Output Plots


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north west preston aimsun microsimulation...

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