A PTAL approach to measuring changes in bus service accessibility

Belinda M. Wu*, Julian P. Hine

Transport and Road Assessment Centre, School of Built Environment, University of Ulster at Jordanstown, Shore Road, Newtonabbey BT37 0QB, UK

Received 1 February 2003; revised 1 June 2003; accepted 1 July 2003

Abstract

Accessible transport systems are essential to ensure equal opportunities for all people in society. The need for information about transport

disadvantage is now a key policy requirement and previous studies have highlighted the need for tools to assess the impact of interventions on

the bus network and the accessibility of the system. Geographical Information System (GIS) and ACCMAP enable the analysis of transport

disadvantage and accessibility. This paper provides an analysis of the Citybus Network in Northern Ireland and assesses the spatial impact of

a hypothetical network change on populations residing within the Citybus network area.

q 2003 Elsevier Ltd. All rights reserved.

Keywords: Bus service; Public transport accessibility levels; Equivalent doorstep frequency

1. Introduction

In future accessibility will be given more weight in land

use and transport decisions (ODPM, 2003). Bus service

provision and the proximity of public transport networks are

important for sections of the population who are more likely

to experience exclusion from goods, services and employ-

ment (Hine and Mitchell, 2001a, 2003; Diaz et al., 2000).

Accessibility planning is a key area of transport policy.

Indeed improved access to bus services is a key cornerstone

of integrated transport strategy. The importance of access to

public transport in order to access local goods and services

has been identified by several studies (DETR, 1998; DETR,

2000; Hine and Mitchell, 2001b; General Consumer

Council for Northern Ireland, 2001; ODPM, 2003). The

consequences of poor access to public transport, which due

to its very nature impacts disproportionately on those with

low incomes, the elderly and women, results in a lack of

ability to access education, jobs, health facilities and

hospitals (Hine and Mitchell, 2001a,b, 2003).

In Belfast car ownership has increased rapidly, and has

as a result produced a gap in terms of access to

opportunities between those with and without access to

private transport. According to the 2001 census 43% of

households in Belfast do not own a car (NISRA, 2003).

The new Regional Transportation Strategy (RTS) has given

a sharper focus on the need for public transport investment

to meet the needs of the socially excluded (DRD, 2002;

Cooper et al., 2001).

In Northern Ireland the sectarian divide is a dimension to

the planning of transport systems that needs to be

considered (Smyth, 2000). Each community, whether

Protestant or Catholic, exhibits distinctive social and

political attributes, values and preferences (Douglas et al.,

1982). It often means that for the delivery of public transport

services, different services have to be operated for different

sections of the community. Members of either community

generally do not wish to be seen using a public transport

service that takes them through other community areas for

reasons of safety and fear of attack, either real or perceived

(Smyth, 2000; Murtagh, 1994). In this paper we have, using

the PTAL approach explored this dimension of public

transport policy.

This paper firstly provides a description of the Belfast

area served by the Citybus network, and secondly the impact

of hypothetical network changes on accessibility (scen-

arios). The paper also looks at the impact of these changes

on different age and religious groupings as measured by the

PTALs approach. These scenarios are: Option 1—current

situation; Option 2—a redeployment of buses to underpin

the development of a metro/overground style network, with

no off peak services; Option 3—consists of metro/over-

gound network as in Option 2 plus a secondary network and

0967-070X/$ - see front matter q 2003 Elsevier Ltd. All rights reserved.

doi:10.1016/S0967-070X(03)00053-2

Transport Policy 10 (2003) 307–320

www.elsevier.com/locate/tranpol

* Corresponding author. Tel.: þ44-2890-366-892.

E-mail address: b.wu@ulster.ac.uk (B.M. Wu).

off-peak services; Option 4—metro/overground network

plus comprehensive secondary network operated through

out the day.

2. GIS and accessibility planning

This study reviews available census data and network

data with the aid of GIS and ACCMAP technology. The

approach adopted includes

† Use of Noble Index of Deprivation to assess levels of

deprivation within the Citybus network spatially.

† Use of GIS and ACCMAP to spatially assess changes in

levels of public transport accessibility, as networks

change.

2.1. Noble index of deprivation

Measures of Deprivation in Northern Ireland study is

carried out by Social Disadvantage Research Centre of

University of Oxford in 2000. It sets out the methodology for

combining the indicators into Domain Deprivation Measures

and for combining the domains into an overall ward level

Multiple Deprivation Measure (MDM). The Noble Index of

Multiple Deprivation used in this study is based on the 1991

Census, and provides insight into the geographical distri-

bution of different forms of deprivation and disadvantage.

The domains of deprivation refer to different types of

deprivation or ways in which deprivation can be experienced.

The measures consist of seven separate types of deprivation

(Social Disadvantage Research Centre, 2001)

† Income domain

† Employment domain

† Health and disability domain

† Education domain

† Geographical access to services domain1

† Social environment domain

† Housing domain

2.2. GIS and ACCMAP

GIS is renowned for its ability to visualise, analyse and

model geographical data. It enables the application of

quantitative geographical methods within a digital environ-

ment. A GIS map can combine many layers of information

that are associated with a linked database. In this study, data

sets are displayed in a range of innovative ways (3-D, Grid,

thematic maps, etc.) to facilitate data interpretation.

Another major activity that complements GIS analysis is

the use and development of network models using

ACCMAP. This journey access and travel time mapping

package measures accessibility to and from any point based

on travel costs through highway and public transport

networks (Citilabs). ACCMAP also provides an accessibility

mapping overlay on any background map to allow the impact

of network changes on the transport system to be clearly

shown. ACCMAP is also a useful tool in the development of

network models. The software also facilitates the production

of Public Transport Accessibility Levels (PTAL) indices for

different public transport service time periods.

2.3. PTALs

The objective in assessing public transport accessibility

is primarily to enable comparisons to be made between

† The relative accessibility which exists at different

locations within the city, and

† The relative effects on such accessibility of introducing

different schedules or levels of service.

Data sets of public transport stop locations, route

delineations and service schedule frequency have to be

populated for the public transport network database to

generate the PTAL indices. Depending on local environ-

mental factors, the input parameters for PTAL generation

can be altered. System defaults were utilized in this paper,

although ‘origin’ and ‘maximum walk distance’ parameters

were selected to meet our own analytical objectives—

namely 250 m (equidistant) and 400 m, respectively.

Public transport accessibility is influenced by the

aggregate availability/quality of public transport services

within a reasonable walking distance, therefore:

Access time ¼ walking time þ average waiting time

¼ walking time þ k þ scheduled waiting time

Where k is a ‘reliability’ factor relating to the reliability of

the service, which may be derived from observed survey

data for each service at any time of day. If services are

operating to schedule then k ¼ 1; however, in the absence of

up-to-date and accurate survey data it has been agreed with

London Transport that k ¼ 0:75 for underground, rail and

tram services and k ¼ 2 for bus services (Citilabs). The

default settings for the reliability factor and weightings for

walking time and the waiting time are used in this study as

advised by the ACCMAP manual.

For each selected route the scheduled waiting time

(SWT) is calculated. This is estimated as half the headway

(i.e. the interval between services,) so SWT ¼ 0.5*

(60/Frequency), hence

Average waiting time ¼ k þ 30=scheduled frequency per hour

Then the Equivalent Doorstep Frequency (EDF) can be

calculated for each route as follows

EDF ¼30

access time

1 Here the access to services does not include public transport services. It

refers to the public services such as post offices and health services.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320308

The aggregate EDF (or the Accessibility Index) for each

location can then be obtained by a summation of all the

individual EDFs within the walking distance (London

Borough of Hammersmith and Fulham, 2000). Having

derived Accessibility Indices for a range of locations

(origins), the indices were then grouped (and spatially

mapped) into six value ranges, and then defined in terms of

Accessibility Levels (i.e. spanning a range of Accessibility

Indices, Table 1).

PTALs are a highly detailed measure of the accessibility

of any origin point to the public transport network, taking

into account the walk access time and service availability.

The method is particularly suited to local area studies in

urban situations and it reflects

† The walking time from the origin point to the public

transport access points.

† The reliability of the service modes available.

† The number of services available within the catchment.

† The level of service at the public transport access

points—i.e. average waiting time.

Level of access to public transport services is therefore a

function of the degree to which social exclusion processes

are experienced. PTALs as indicators are of particular

importance in revealing the impact of network changes on

travel patterns for those groups who rely on bus provision.

PTAL analysis has been increasingly used throughout the

UK since the original methodology was developed and

thoroughly tested by London Borough of Hammersmith and

Fulham (1992) and Hardcastle and Cleve (1995) for

example. The main strength of the approach is that it is

easy to understand. Unlike traditional modelling

approaches, PTALs provide a direct visualization of data

using the coloured contour map in which patterns of

provision are clearly shown. PTALs can provide useful

indicators to facilitate strategic planning. For example, in

assessing whether a change of services is acceptable,

proposals can be considered in the light of such factors as

PTALs to evaluate potential changes that could hinder

social inclusion objectives. PTALs can also be used to

identify areas where public transport accessibility is high.

While providing a useful indicator of local accessibility

and comparative studies, this approach does assume that

access to the public transport network provides access to

reasonably well integrated rail and bus services within the

urban context and consequently a range of final destinations.

This is a reasonable assumption to make for a city such as

Belfast, a city with a reasonably comprehensive public

transport network. However, in rural areas the method may

not be applicable where there may only be a limited number

of routes with poor connections and interchange facilities.

Other criticisms of the method are that it does not consider

aspects of travel time such as speed of service, congestion,

crowding, stopping/express services and ease of

interchange.

3. The Citybus network

Citybus, Northern Ireland Railways and Ulsterbus are

the three operating subsidiaries of Northern Ireland

Transport Holding Company (NITHC). NITHC and

operate bus and rail public transport services under the

group name Translink. Citybus was formed in 1973 from

the Belfast Corporation Transport undertaking and it

operates approximately 60 routes in Belfast. It maintains

a fleet of over 250 buses to provide services from 04:00

in the morning till 24:00, and provides additional peak

hour journeys during the Morning Peak and Evening Peak

for passengers who are going to or leaving school/work

(Fig. 1).

The Citybus service area is divided into five sectors,

these are

† The Inner Zone serving the City Centre area,

† Sector 1 serving northwest areas such as Springmartin,

Glencairn, Ligoniel, Silverstream, Carrs Glen, Oldpark

and Downview,

† Sector 2 serving southwest areas such as Falls Park, Turf

Lodge, Glencolin, Lenadoon, Ladybrook, Malone, Erin-

vale, Balmoral, Stranmillis, Ormeau, Annadale and Four

Winds,

† Sector 3 serving southeast areas such as Creagagh,

Gilnahirk, Mann’s Corner, Braniel and Stormont, and

† Newtownabbey Sector serving Networnabbey areas

such as Greencastle, Hydepark, Ballyhenry, Mossley,

Carnmoney and Ballyduff (Fig. 2).

Some of the deprived wards in the network are not only

the most deprived according to the Noble Index of

Deprivation, but are also disadvantaged in terms of public

transport access. They are found within the ‘very poor/poor’

PTAL zones. In Fig. 3 we can see that five of the most

deprived areas are located in the centre of the Citybus

network. Three of them are included in the ‘moderate’ or

better PTAL zones, however, the other two are still in the

‘poor/very poor’ zones. With lower multiple deprivation

rankings, residents in these areas are more likely to rely on

Table 1

Accessibility levels

Accessibility level Range of accessibility Indices

1. Very poor 0.00–5.00

2. Poor 5.01–10.00

3. Moderate 10.01–15.00

4. Good 15.01–20.00

5. Very good 20.01–25.00

6. Excellent .25.00

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320 309

public transport services. Hence, Citybus is of particular

importance to these people.

A Grid Map and a 3-D map have been generated on the

basis of the morning peak PTALs to provide a direct visual

comparison of the accessibility of the current network

(Fig. 4). Both maps indicate higher levels of accessibility

around the City Centre area. However, due to operational

reasons, accessibility levels decline gradually from the City

Centre to suburbs. In some areas moderate or more

accessible PTAL zones have extended into the suburban

Fig. 1. Average number of buses in use by hour-citybus.

Fig. 2. Citybus service area. Fig. 3. Deprived areas within the current network.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320310

areas. In the south such an extension relates to the Quality

Bus Corridor (QBC), that was introduced in 2000. This

operates on the main arterial route from the south side of

Belfast. Bus services are of a higher frequency in this

corridor as a result (Fig. 4).

3.1. Population structure and car ownership

in the citybus area

The 1991 census data at the ward level is used in

combination with the PTALs for our analyses in this study.2

Analysis of the population structure reveals that the majority

of residents in the Citybus area live in areas, where provision

according to PTAL zones is poor/very poor. The Citybus

network is more accessible in the morning peak and between

peak periods, while in the evening peak and off peak the

accessibility levels decline. In the morning peak, 118,078

people (this is 60.46% of the total population) reside in the

poor/very poor PTAL zones. 18.32% of the people according

to the analysis have ‘good’ or even better access to Citybus

Services. This situation continues into the between peak

time. Accessibility declines during the evening peak when

the percentage of people without access to Citybus services

increases by about 10%. In fact the percentage of people who

have good access drops to 10.42% of the population. A

further decline of accessibility is found in the off peak period

during which almost 90% of the total population do not have

good access to Citybus network (Table 2).

Analysis of car ownership found that around 58% of the

households within the Citybus service area do not possess

a car. These households rely on public transport although the

analysis indicates that they do not have satisfactory access to

Citybus services. More than 15% of the households in the

poor/very poor PTAL zones were found to have no access to

cars in all time periods except during the evening peak.

In the morning peak 16.46% of total households that do

not have a car are within the poor/very poor PTAL zones.

PTALs in the between peak time period indicate that this

same situation continues during this period. There is some

improvement in the evening peak where only 6.88% of the

households that do not have a car are less well served.3

However, in the off peak time this proportion of households

increases rapidly to 24.36% of non car owning households

without access to cars in the poor/very poor PTAL zones

and makes the poorest accessibility of the day (Table 2).

4. Network changes and the impact

Consider the current Citybus network as the baseline/

Option 1, three hypothetical networks are generated to assess

the impact of the network changes, namely Option 2–4.

Fig. 4. 3-D map—the current network PTAL.

2 The 1991 census data in NI was the most up-to-date data at the time this

study was conducted.

3 The reason that the figure for car ownership seems to vary by time of

day is actually because the PTAL zones vary in time period and include

different households. Such changes also affect the population analysis.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320 311

4.1. Routes changes

In the map above, the hypothetical networks have

fewer service routes than the current network and will

therefore reduce the accessibility greatly in the remaining

area. As a result of the reduction of routes, the

hypothetical networks all cover a smaller service area.

The Newtownabbey Sector, Sector 1–3 all show a great

reduction in service area. The decline in number of

services is also shown in the map by the density of the

routes. Of particular importance is the reduction of the

Citybus routes/services in Sector 1 and 3, where the five

most deprived areas are located. The population in these

areas are more likely to have no access to the private car

and therefore rely heavily on the public transport services

for their travel. With the level of accessibility decreasing,

residents of areas such as Crumlin, Whiterock, New

Lodge, the Mount and Shankill would clearly be affected

in terms of the access to education, jobs, health facilities

and hospitals (Fig. 5).

4.2. PTAL changes

Network accessibility is assessed by the PTALs for

the four main periods of time in a day. This is generated

on the basis of a maximum 400 m walk distance. From

the current network PTAL maps, we can see that the

accessibility of the Citybus services in the City Centre

area is very good throughout the day. Areas with

moderate or better accessibility levels extend into the

outskirts and suburbs of the city. Such areas in the south

of the network are of particular importance in building

up the QBC. The accessibility levels of the current

network are especially good during Morning Peak and

Table 2

Population structure within citybus service area

PTAL zone Population structure Car ownership

0_15 16_59 60 þ z%Tot* zTotal* Total* NoCar %Tot* 1Car 2Car 3Car

Morning peak

Very poor 13,390 31,732 10,340 28.4 55,462 185 117 10.58 51 16 1

Poor 13,866 36,122 12,628 32.06 62,616 142 65 5.88 62 12 3

Moderate 9091 24,017 8420 21.22 41,455 207 84 7.59 100 21 2

Good 5207 14,200 5205 12.6 24,612 192 136 12.3 54 2 0

Very good 1745 4317 1535 3.89 7597 185 85 7.69 88 8 4

Excellent 710 2020 842 1.83 3572 195 153 13.83 40 2 0

Network total 44,009 112,424 38,970 100 195,314 1106 640 57.87 395 61 10

Between peak

Very poor 13,390 31,732 10,340 28.4 55,462 185 33 2.95 108 39 5

Poor 13,866 36,122 12,628 32.06 62,616 189 158 14.15 29 2 0

Moderate 9019 24,017 8420 21.22 41,455 185 93 8.33 77 12 3

Good 5207 14,200 5205 12.6 24,612 142 65 5.82 62 12 3

Very good 1745 4317 1535 3.89 7597 200 31 2.78 70 80 19

Excellent 710 2020 842 1.83 3572 216 189 16.92 25 2 0

Network total 43,937 112,408 38,970 100 195,314 1117 569 50.94 371 147 30

Evening peak

Very poor 13,206 32,235 10,277 32.33 55,718 186 23 2.11 117 39 7

Poor 14,884 37,614 12,568 37.77 65,075 194 52 4.77 114 27 1

Moderate 7142 19,267 7144 19.47 33,553 142 65 5.96 62 12 3

Good 2310 6028 2127 6.07 10,465 185 95 8.71 80 10 0

Very good 959 2680 981 2.68 4620 198 108 9.9 80 9 1

Excellent 575 1610 715 1.68 2899 186 148 13.57 35 3 0

Network total 39,076 99,434 33,812 100 172,329 1091 491 45 488 100 12

Off peak

Very poor 14,334 36,390 12,419 50.15 63,143 185 117 15.66 51 16 1

Poor 10,548 27,928 9558 38.15 48,034 142 65 8.7 62 12 3

Moderate 1974 5661 2094 7.72 9729 185 95 12.72 80 10 0

Good 546 1460 649 2.11 2654 216 189 25.3 25 2 0

Very Good 120 535 189 0.67 844 19 13 1.74 5 1 0

Excellent 323 863 318 1.2 1505 0 0 0 0 0 0

Network total 27,845 72,837 25,226 100 125,908 747 479 64.12 223 41 4

Note: zTotal, total population in the PTAL zone; z%Tot, percentage of zonal total population in the network total; total, total car number in the PTAL zone;

%Tot, percentage of zonal total households without a car in the network total.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320312

Evening Peak. Even in the suburbs, areas within

Newtownabbey Sector and some Southwest areas in

Sector 2 have a moderate level of access to the bus

network. Accessibility levels during the between peak

and off peak are lower than during the peak time, due to

the different shape and nature of transport demand at this

time. However, even during the off peak time period

where provision is at its poorest, there is still a full range

of six levels of accessibility. In other words, even during

the off peak, some areas still have ‘very good/excellent’

access (Fig. 6).

Option 2 is based on the redeployment of buses

currently used in the off peak in order to provide a higher

service frequency on the network of proposed ‘metro/o-

verground’ routes. Under this proposal additional morning

and evening peak hour journeys could be provided before

and after school/work. This option however, does not

include off peak services. Services are only provided

during three periods: morning peak, between peak and

evening peak.

PTAL zones for Option 2 present a picture of much

poorer accessibility for the Citybus service area. This

option also includes a reduction in the size of the service

area. A major cut in the service area is found in Sector

3, where the area is reduced to approximately 1/3 of the

current size. Another main reduction of the area in

Sector 2 leaves only about 1/2 of the original area. As

we discussed previously these two service sectors include

the five most deprived areas in the network, these areas

are also among the 10 most deprived areas in the whole

Northern Ireland. All sectors experience a reduction in

the service area to different degrees. In the remaining

areas, accessibility to Citybus services is also reduced

greatly. The PTALs of the morning peak and evening

peak and those of the between peak are very similar in

this option. Accessibility of Citybus services during the

peak time therefore may need to be strengthened, as the

travel demand at those times is likely to be much greater.

Off peak services are not considered in the Option 2

design (Fig. 7).

Option 3 is based on the redeployment of buses from the

off peak to services on the ‘Metro’ network and a secondary

system of services to infill the area covered. Minibuses may

provide additional local services during the between peak

and extra morning and evening peak journeys would also be

provided. This option includes services in all four main time

periods of a day: morning peak, between peak, evening peak

and off peak.

From the PTAL maps, it can be seen that overall, with

the aid of minibus services, hypothetical network Option 3

covers a larger service area and provides a better

accessibility to the Citybus services area than Option 2.

However, it is still not an improvement in comparison with

the current network. The total service area is smaller and

Fig. 5. Routes changes.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320 313

accessibility in the remaining area is not as satisfactory as

in Option 1. All sectors receive a decrease in the service

area, although not as great as in Option 2. In this option,

the area with good access to Citybus services shrinks

towards the City Centre. Unlike the reduction of the area in

Newtownabbey Sector, the reduction made in the south-

west part in Sector 2 and 3 will have a significant impact

on residents in those deprived areas within Sector 3. Such

impact may reflect to a greater degree the lower levels of

car ownership within them. However, Option 3 shows

an extension of the service area in the southern part, such

changes in the south may strengthen the QBC services.

During the off peak, the accessibility level declines when

compared to PTALs of Option 1 during the same period of

time. Only a much smaller area is covered and the only

area that has the accessibility level of good is the very

centre of the city. There are only four levels of accessibility

in this period, that is, none of the zones within the

hypothetical network will have accessibility at the level of

‘very good’ or ‘excellent’. Similar to Option 2, the design

Fig. 6. Current network—ptal zones.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320314

of Option 3 needs to be optimised to provide efficient bus

services during the peak time (Fig. 8).

Option 4 is based on the redeployment of buses

currently used off peak to provide services on the Metro

Network with buses and minibuses to provide a compre-

hensive additional secondary network operating throughout

the day. School services would still not be provided. This

option includes services in all four main time periods of a

day as well.

The Citybus network Option 4 is a further improve-

ment of Option 3 in terms of PTALs. However, it still

cannot provide the same levels of accessibility for

the Citybus services as experienced at the present time,

except on the QBC Services. This option covers a similar

size of total service area as in Option 3, and accessibility

in the south of Sector 2 also improves. There are no very

good or excellent levels of accessibility for the off peak

Citybus services as in other hypothetical options. It

indicates a sharp decline in levels of access when

compared to the PTALs for the current network.

Comparison of PTALs for different periods of the day

in Option 4 again shows little variation in the accessibility

of services during the peak and other periods of time,

unlike the current network. The efficiency of the peak

Fig. 7. Option 2—PTAL zones.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320 315

time service needs to be addressed, as a greater level of

travel demand will be generated during the morning peak

or evening peak (Fig. 9).

4.3. Impact on population structures

In order to monitor population change within the

Citybus network, we have compared the residential counts

from the different network options during four main

periods of the day. All three hypothetical network designs

result in a loss of population in their respective service

areas to different degrees. The loss reflects a reduction in

the proportion of the population that is in proximity to the

bus network. In this analysis, results of Option 4 are not

listed, as they are similar to those of Option 3. During the

morning peak, the remaining population in poor/very poor

Fig. 8. Option 3—PTAL zones.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320316

PTAL zones increases significantly, with the percentages

of population in those zones rising rapidly from 60.46 to

92.36% in Option 2 and 80.92% in Option 3, respectively.

On the other hand, less than 2.4% of the residents will

have very good or excellent access to the network in all

the hypothetical options discussed in this paper. Com-

pared to 5.72% of residents in the current network. The

analysis indicates a poorer accessibility in the previously

more accessible zones PTAL zones as well as in those

previously poorer PTAL zones. Similarly, results suggest

the same degree of impact during between peak and

evening peak. The population also decreases in the PTAL

zones with higher levels of accessibility, while it increases

in the PTAL zones with lower levels of access. Option 2

does not consider services in the off peak. In Option 3,

however, 94.86% of the total population will be in the

‘very poor’ PTAL zones and only 1.59% of the population

within the network area will have moderate or a better

Fig. 9. Option 4—PTAL zones.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320 317

level of accessibility to the off peak Citybus services

(Table 3).4 Data analysis has shown that for residents

aged over 60 services take up about 20% of the total

population. However, the accessibility of the Citybus

services for them is far from adequate in the hypothetical

options. During the morning peak, older people in the

very poor/poor PTAL zones increase by more than 20% in

all options, while the percentage of older people who have

good or better access to the bus network drops by about

16%. Similar percentages are found during the between

peak and evening peak. Accessibility is even poorer in the

off peak, none of the older residents have good or above

levels of accessibility to Citybus services, as the analysis

results from Option 3 reveal (Option 2 does not provide

services in this period) (Table 3).

4.4. Impact on different religion groupings

Religious segregation in Northern Ireland makes it

difficult for individuals to travel to work or training through

areas, where the other community is resident. Lack of access

to Citybus is therefore a function of social exclusion and in

order not to deprive people of the opportunity of training,

employment and social interaction, the accessibility of the

Citybus in these areas needs to be improved. The impact of

network changes on different religious groups has been

analysed using the PTAL approach. Both Roman Catholic

and Protestant populations experience changes in levels of

accessibility to the Citybus network (Table 4). Analysis

indicates an increase in proportions are served in the

morning peak for Protestants, while an improvement in

accessibility for Roman Catholics is found during the

evening peak in all hypothetical options. In the between

peak and off peak periods both communities will experience

lower accessibility levels in all the three network options.

In the morning peak, more than 80% of Roman Catholics

will have at least moderate levels of access in all options,

while Protestants will experience improved accessibility in

all hypothetical options. The proportion of people in poorer

PTAL zones declines continuously, while the percentage in

better PTAL zones increases significantly. The evening

peak PTALs, however, suggest a different situation. For

Table 3

Impact on population structure

PTAL zone Option 1 Option 2 Option 3

Total %Tot 60 þ %60 þ Total %Tot 60 þ %60 þ Total %Tot 60 þ %60 þ

Morning peak

Very poor 55,462 28.40 10,340 26.53 50,057 57.21 10,119 57.84 57,121 45.71 10,949 45.5

poor 62,616 32.06 12,628 32.4 30,760 35.15 5862 33.51 44,002 35.21 8600 35.74

Moderate 41,455 21.22 8420 21.61 3135 3.58 674 3.85 18,992 15.20 3301 13.72

Good 24,612 12.60 5205 13.36 1473 1.68 355 2.03 1916 1.53 505 2.1

Very good 7597 3.89 1535 3.94 1235 1.41 295 1.69 1473 1.18 355 1.48

Excellent 3572 1.83 842 2.16 844 0.96 189 1.08 1473 1.18 355 1.48

Total 195,314 100 38,970 100 87,504 100 17,494 100 12,4977 100 24,065 100

Between peak

Very poor 55,462 28.40 10,340 26.53 50,057 57.91 10,119 57.64 54,690 42.91 10,641 43.55

Poor 62,616 32.06 12,628 32.4 30,760 35.59 5862 33.39 46,814 36.73 8970 36.71

Moderate 41,455 21.22 8420 21.61 3135 3.63 674 3.84 20,498 16.08 3621 14.82

Good 24,612 12.60 5205 13.36 166 0.19 355 2.02 2405 1.89 491 2.01

Very good 7597 3.89 1535 3.94 1473 1.70 355 2.02 1560 1.22 356 1.46

Excellent 3572 1.83 842 2.16 844 0.98 189 1.08 1473 1.16 355 1.45

Total 195,314 100 38,970 100 86,435 100 17,554 100 12,7440 100 24,434 100

Evening peak

Very poor 55,718 32.33 10,277 30.39 50,057 55.69 10,119 56.2 56,262 45.96 11,061 46.27

Poor 65,075 37.76 12,568 37.17 33,052 36.77 6381 35.44 46,023 37.59 8876 37.13

Moderate 33,553 19.47 7144 21.13 3218 3.58 667 3.7 15,162 12.38 2808 11.75

Good 10,465 6.07 2127 6.29 1473 1.64 355 1.97 2034 1.66 450 1.88

Very good 4620 2.68 981 2.9 1235 1.37 295 1.64 1473 1.20 355 1.49

Excellent 2899 1.68 715 2.11 844 0.94 189 1.05 1473 1.20 355 1.49

Total 172,329 100 33,812 100 89,879 100 18,006 100 12,2427 100 23,905 100

Off peak

Very poor 63,143 50.15 12,419 49.23 50,408 94.86 10,284 93.96

Poor 48,034 38.15 9558 37.89 1888 3.55 472 4.31

Moderate 9729 7.73 2094 8.3 844 1.59 189 1.73

Good 2654 2.11 649 2.57 0.00 0 0

Very good 844 0.67 189 0.75 0.00 0 0

Excellent 1505 1.20 318 1.26 0.00 0 0

Total 125,908 100 25,226 100 53,140 100 10,945 100

4 See footnote 3.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320318

the Roman Catholic population accessibility is improved

while Protestants experience a decline of accessibility in all

hypothetical options. During the between peak and off peak,

the decline in accessibility hits both communities. In Option

2, percentage of people in poor/very poor zones rises from

16.56 to 59.56% for Catholic, and a rises from 37.96 to

58.48% for Protestants during the between peak. No

Catholics or Protestants have good or better access to the

off peak services in Option 3 and 4 and there is no off peak

service in Option 2 (Table 4).

5. Conclusion

By mapping the accessibility of the Citybus network, the

spatial impact of the network changes is clearly shown. In

general, all three hypothetical networks discussed in the

paper cover smaller service areas. As a result the accessibility

is not as satisfactory as in the current network. Data analysis

shows that Option 2 is the least accessible of all hypothetical

designs. It covers the smallest Citybus service area and does

not provide Off Peak services. Most areas that remain in this

option will be in the Very Poor/Poor PTAL zones. Option 3

and 4 both show improvement on the basis of Option 2 and

improvements in the south of the network which strengthen

the ‘QBC’ services. However, both options have poorer

accessibility compared to the current network. Little

variation is shown between the PTAL maps of the Morning

Peak and Evening Peak and those of the Between Peak in all

hypothetical options. It may indicate pressure on peak time

services, due to the greater travel demand during the Morning

Peak and Evening Peak.

Different hypothetical network options are compared in

terms of the impact on population structure, car ownership

and religious groupings using the data stored in the

databases within the GIS. The analysis indicates that the

hypothetical network changes have a disproportionate

impact on older people as well as other age groups.

Households with no car are found to have poorer access to

bus services in the Morning Peak and Off Peak. For

Table 4

Impact on religion groupings

PTAL zone Option 1 Option 2 Option 3 Option 4

RC %RC PR %PR RC %RC PR %PR RC %RC PR %PR RC %RC PR %PR

Morning peak

Very poor 46 2.43 203 26.96 103 5.04 296 46.76 149 14.40 127 11.91 110 8.87 191 22.98

Poor 61 3.22 226 30.01 555 27.14 1 0.16 10 0.97 311 29.17 10 0.81 311 37.42

Moderate 41 2.16 320 42.5 830 40.59 1 0.16 830 80.19 1 0.09 508 40.97 0 0.00

Good 649 34.25 3 0.4 39 1.91 181 28.59 1 0.10 299 28.05 567 45.73 1 0.12

Very good 531 28.02 0 0 475 23.23 122 19.27 2 0.19 296 27.77 2 0.16 296 35.62

Excellent 567 29.92 1 0.13 43 2.10 32 5.06 43 4.15 32 3.00 43 3.47 32 3.85

Total 1895 100 753 100 2045 100 633 100 1035 100 1066 100 1240 100 831 100

Between peak

Very poor 77 16.56 301 19.33 103 7.19 296 57.14 110 4.42 191 54.89 110 14.82 191 17.36

Poor 0 0 290 18.63 750 52.37 7 1.35 764 30.68 2 0.57 10 1.35 311 28.27

Moderate 79 16.99 248 15.93 497 34.71 2 0.39 531 21.33 0 0.00 10 1.35 269 24.45

Good 61 13.12 226 14.52 39 2.72 181 34.94 567 22.77 1 0.29 567 76.42 1 0.09

Very good 247 53.12 193 12.4 43 3.00 32 6.18 475 19.08 122 35.06 2 0.27 296 26.91

Excellent 1 0.22 299 19.2 0.00 0 0.00 43 1.73 32 9.20 43 5.80 32 2.91

Total 465 100 1557 100 1432 100 518 100 2490 100 348 100 742 100 1100 100

Evening peak

Very poor 120 43.96 343 20.98 103 5.04 296 46.76 110 4.42 191 54.89 149 17.05 127 12.44

Poor 27 9.89 345 21.1 555 27.14 1 0.16 764 30.68 2 0.57 103 11.78 296 28.99

Moderate 61 22.34 226 13.82 830 40.59 1 0.16 531 21.33 0 0.00 10 1.14 269 26.35

Good 52 19.05 177 10.83 39 1.91 181 28.59 567 22.77 1 0.29 567 64.87 1 0.10

Very good 10 3.66 269 16.45 475 23.23 122 19.27 475 19.08 122 35.06 2 0.23 296 28.99

Excellent 3 1.1 275 16.82 43 2.10 32 5.06 43 1.73 32 9.20 43 4.92 32 3.13

Total 273 100 1635 100 2045 100 633 100 2490 100 348 100 874 100 1021 100

Off peak

Very poor 46 11.33 203 21.66 0 0.00 502 76.52 0 0.00 502 76.52

Poor 61 15.02 226 24.12 475 91.70 122 18.60 475 91.70 122 18.60

Moderate 52 12.81 177 18.89 43 8.30 32 4.88 43 8.30 32 4.88

Good 1 0.25 299 31.91 0.00 0 0.00 0.00 0 0.00

Very good 43 10.59 32 3.42 0.00 0 0.00 0.00 0 0.00

Excellent 203 50 0 0.00 0.00 0 0.00 0.00 0 0.00

Total 406 100 937 100 518 100 656 100 518 100 656 100

Note: RC, Roman Catholic; PR, Protestant; %RC, percentage of total Catholic; %PR, percentage of total Protestant.

B.M. Wu, J.P. Hine / Transport Policy 10 (2003) 307–320 319

the Protestant community, Option 2–4 mean that they are

increasingly well served in the morning peak, while an

improvement for Roman Catholics is found during the

evening peak in all hypothetical options. In the between

peak and off peak both communities are hit by lower

accessibility levels in all hypothetical network options.

Previous studies have highlighted the need for tools to

assess the impact of interventions on the bus network and the

accessibility of the system. Using Geographic Information

Systems and ACCMAP, the analysis of transport disadvantage

and accessibility is possible. This paper provides an analysis of

the Citybus network in Northern Ireland and assesses the

spatial impact of hypothetical network changes on populations

residing within the Citybus network area. Within the GIS

environment, data sets are displayed in a range of innovative

ways (3-D, Grid and other thematic maps) to facilitate data

interpretation. The use of ACCMAP allows the development

of network models and it also facilitates the strategic analysis

of existing and proposed public transport services through the

production of PTALs in different time periods.

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