Project Appraisal Guidelines for
National Roads Unit 16.1 Expansion Factors for Short Period
Traffic Counts
PE-PAG-02039
October 2016
TRANSPORT INFRASTRUCTURE IRELAND (TII) PUBLICATIONS
About TII
Transport Infrastructure Ireland (TII) is responsible for managing and improving the country’s
national road and light rail networks.
About TII Publications
TII maintains an online suite of technical publications, which is managed through the TII Publications
website. The contents of TII Publications is clearly split into ‘Standards’ and ‘Technical’
documentation. All documentation for implementation on TII schemes is collectively referred to as
TII Publications (Standards), and all other documentation within the system is collectively referred to
as TII Publications (Technical).
Document Attributes
Each document within TII Publications has a range of attributes associated with it, which allows for
efficient access and retrieval of the document from the website. These attributes are also contained
on the inside cover of each current document, for reference.
TII Publication Title
Project Appraisal Guidelines for National Roads Unit 16.1 Expansion Factors for Short Period Traffic Counts
TII Publication Number
PE-PAG-02039
Activity
Planning & Evaluation (PE)
Document Set
Select Document
Set
Stream
Project Appraisal Guidelines
(PAG)
Publication Date
October 2016
Document
Number
02039
Historical
Reference
PAG Unit 16.1
TII Publications Website
This document is part of the TII publications system all of which is available free of charge at
http://www.tiipublications.ie. For more information on the TII Publications system or to access further
TII Publications documentation, please refer to the TII Publications website.
TII Authorisation and Contact Details
This document has been authorised by the Director of Professional Services, Transport
Infrastructure Ireland. For any further guidance on the TII Publications system, please contact the
following:
Contact:
Postal Address:
Telephone:
Email:
Standards and Research Section, Transport Infrastructure Ireland
Parkgate Business Centre, Parkgate Street, Dublin 8, D08 DK10
+353 1 646 3600
[email protected]
TRANSPORT INFRASTRUCTURE IRELAND (TII) PUBLICATIONS
TII Publications
Activity:
Planning & Evaluation (PE)
Stream:
TII Publication Number:
Project Appraisal Guidelines (PAG)
Project Appraisal Guidelines for National Roads Unit 16.1
- Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
Publication Date:
October 2016
Set:
Select Document Set
TII Publication Title:
Contents Table
Glossary ............................................................................................................................... 1
1. Overview ...................................................................................................................... 2 2. Factors Effecting Traffic Flow Profiles ...................................................................... 4 3. Overview of the Generic Expansion Factor Method................................................. 5 4. Factoring by Hour of Day ........................................................................................... 6 5. Factoring by Day of Week ........................................................................................ 12 6. Factoring by Month of Year ...................................................................................... 13 7. Dealing with Multiple Datasets ................................................................................. 15 Appendix A: ....................................................................................................................... 16 Sample Traffic Flow Profiles (2015) ..................................................................................... 16 Appendix B: ....................................................................................................................... 30 Weekly Flow Indices ............................................................................................................ 30 Appendix C: ....................................................................................................................... 33 Monthly Flow Indices ........................................................................................................... 33 Page i
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
Glossary
AADT
Annual Average Daily Traffic
TMU
Traffic Monitoring Unit (TII Permanent Traffic Counter)
WADT
Weekly Average Daily Traffic
Definitions
Annual Average Daily Traffic (AADT)
The total two-way traffic volume passing a point or segment of a road for one full calendar year,
divided by the number of days in a year (365).
Weekly Average Daily Traffic (WADT)
The total two-way traffic volume passing a point or segment of a road for one full week (Monday to
Sunday) divided by the number of days in the week (7).
Average Weekday Traffic
The total two-way volume passing a point or segment of a road for one full working week (Monday to
Friday) divided by the number of days in the working week (5).
Generic Expansion Factor Method
A method of extrapolating short period traffic counts to longer periods, or to other count periods
using a series of standard indices.
Traffic Flow Profile
The shape of a line plot of hourly traffic flow across a 24-hour period, with hourly traffic flow
expressed as a proportion of the total daily flow
Page 1
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
1.
Overview
The planning and appraisal of any proposed works on the national road network requires an
understanding of the traffic demand that will be supported by such improvements. This ensures that
the proposed works can accommodate the anticipated demand, and allows the quantification of
benefits as part of the scheme appraisal.
This PAG Unit has been prepared to support the conversion of Short Period Traffic Counts to AADT,
or to facilitate the estimation of short period traffic flows at any point in a year using only a sample
dataset of traffic information. The guidance achieves this by developing an annual traffic flow profile
that considers time of day, day of week and month of year, thereby generating a series of indices to
allow short period traffic counts from one period to be extrapolated to any period of the year, or to
AADT. This is referred to as the Generic Expansion Factor Method.
The Generic Expansion Factor Method can be used for short period traffic counts where nearby data
is not available, (however with the current network of TMU sites available, it is unlikely that data will
not be available) and where the collection of localised period counts is not justified. This would
normally be the case where data is required for high level studies only, and where outputs will not be
used as the basis for Project Appraisal or any form of local capital investment. For all other
applications, please refer to PAG Unit 16.0: Estimating AADT on National Roads.
PAG Unit 16.0: Estimating AADT on National Roads sets out a methodology for calculating AADT
using short period traffic counts for input to scheme design and appraisal. That Unit describes a
series of options for additional data collection in order to convert localised short period traffic counts
or traffic model outputs into AADT.
This guidance acknowledges the potential for statistical error in the Generic Expansion Factor
Method. Confidence limits are set out where appropriate to ensure that the variability in observations
can be considered.
For the purpose of this PAG Unit, short period traffic counts are defined as counts of duration less
than 14 days. The flowchart in Figure 16.1.1 should be used to inform the most appropriate means
of developing AADT estimates from short period traffic counts in different circumstances.
Page 2
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
Figure 16.1.1: Approaches for estimating AADT from short period traffic counts
Page 3
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
2.
Factors Effecting Traffic Flow Profiles
The conversion of short period traffic counts to alternative short periods or to AADT is dependent on
the shape of the traffic flow profile across a defined period. Flatter traffic flow profiles indicate a more
uniform distribution of traffic flow across a particular period, whilst roads with a more pronounced
increase in traffic flow during particular hours, days or months will lead to increased variability in the
traffic flow profile.
This is indicated below in Figure 16.1.2, with two flow counters data represented. The blue profile
shows a distinct peak in traffic flow during the AM and PM Peak periods, with very low flows
overnight and a notable reduction in flow during the middle of the day. The profile shown in red
shows a lower peak effect, with higher proportional flows during the middle of the day and overnight.
This demonstrates the impact of the daily flow profile on the validity of expansion factors used to
generate daily traffic flow estimates from short period traffic counts during the day.
Figure 16.1.2: Daily Traffic Flow Profiles
Traffic Flow Profile ‐ Weekday
0.10
Proportion of Total Daily Flow
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Hour Beginning
In recognition of this, it is therefore necessary that this variability is considered in the development of
indices to be applied to short period traffic counts. In this regard, PAG Unit 16.0: Estimating AADT
on National Roads highlighted that the following factors influence the generation of indices for
expansion of short period traffic counts:

Geographical Location;

Month of Year;

Day of Week; and

Seasonality.
For the Generic Expansion Factor Method, the effects of these criteria will also be incorporated into
the preparation of indices.
Page 4
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
3.
Overview of the Generic Expansion Factor Method
The conversion of short period traffic counts to alternative periods, and to facilitate an outline
estimation of AADT is based on the following datasets:

Hour of Day: A series of traffic flow profiles that are representative of weekdays for
different geographical regions;

Day of Week: Indices that allow the conversion of a single 24-hour traffic flow to an
average day for that week (WADT); and

Month of Year: Indices that allow the conversion of WADT into an estimate of
AADT.
Although the use of these datasets has been presented to convert short period traffic counts
upwards to AADT, they can equally be used to convert between different short periods thorough
calculation of AADT, followed by inverted use of indices to estimate traffic flow for any short period.
Page 5
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
4.
Factoring by Hour of Day
24-hour traffic flow profiles have been developed based on a series of geographical regions. In order
to define regions, it was necessary to develop an indicator of the shape of the flow profile over a
typical day.
The shape of a daily flow profile can either be described as ‘peaky’ or ‘flat’. Peaky flow profiles
exhibit high traffic volumes during AM and PM Peak periods, with relatively lower flow throughout
the remainder of the day (shown as blue in Figure 16.1.2). This pattern is most evident on busy
commuting corridors, with a limited number of non-employment related uses to generate ongoing
demand throughout the day.
Flat profiles exist for a number of reasons. Congested roads can exhibit relatively flat profiles. The
existence of a capacity constraint during peak periods can lead to spreading of peak demand into
the peak shoulders, effectively restraining the peak flow whilst increasing the off-peak flows. In the
most severe cases, the existence of bottlenecks or opposing movements downstream can lead to a
significant reduction in traffic flow during the peak periods. This can skew the results of any
expansion of peak hour flows quite considerably, and supports the conclusion that the use of short
period traffic flows during congested periods should not be used as the basis for any estimation of
WADT or AADT.
Nevertheless, flat profiles may also suggest that there is a broader range of trip purposes along a
corridor, with commuting demand during the peak periods overlaid with retail, leisure or other
business demands during the off peak periods. As such, flatter flow profiles can easily exist where
there are no significant capacity limitations.
Finally, the use of flow profiles is not appropriate on routes where variable price tolling is employed
(such as the Dublin Port Tunnel). In such cases, the variable pricing of tolls influences demand and
traffic volumes can deviate significantly from the traffic flow profiles presented here.
In order to represent the ‘Peakiness’ of a traffic flow profile over a particular day, the concept of a ‘pfactor’ has been derived. The p-factor simply describes the scale of the reduction in flow between
the AM Peak and the quietest period of the afternoon (the Inter-Peak), and from the Inter-Peak back
up to the PM Peak. It is defined as follows:
p = a + b - 2c
where:
p = the peak factor (known as p-factor)
a = the maximum hourly proportion of traffic between 0:00 and 12:00 on a weekday
b = the maximum hourly proportion of traffic between 12:00 and 24:00 on a weekday
c = the minimum hourly proportion of traffic between 08:00 and 18:00 on a weekday
Consider the example in Figure 16.1.3. The values for a, b, and c are shown on the graph. The pfactor yields a value of 0.057. Note that the maximum p-factor is 1.0, in which case all traffic flow
would occur during 2 individual peak hours of the day, separated by a cessation of all traffic during
the afternoon. The minimum possible theoretical value is zero.
Page 6
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
Figure 16.1.3: Calculation of p-factor
Traffic Flow Profile
Hourly Flows expressed as a proportion of Daily Flow
0.100
b = 0.090
Proportion of Total Daily Flow
0.090
a = 0.077
0.080
0.070
0.060
0.050
c = 0.055
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23
Hour Beginning
In order to understand the impact of geographical location on the p-factor, and hence the traffic flow
profile, p-factors at each TII TMU have been calculated. Figure 16.1.4 presents a frequency plot of
values over the range of p-factors from 0 to 0.15.
The analysis of p-factors demonstrates that the data shows a mean value of 0.071 with a standard
deviation of 0.016.
Page 7
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
Figure 16.1.4: Distribution of p-factor at TII TMU Sites
Distribution of p‐factor at TII Sites
120
Mean = 0.071
St Dev = 0.016
Frequency
100
80
60
40
20
0
0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1 0.11 0.12 0.13 0.14 0.15
p‐factor
As a further exercise, the range of p-factors has been plotted thematically to understand the
influence of geography. This is presented in Figure 16.1.5 and shows high p-factor values as
red/yellow, with lower values in blue. Mid-range values are shown as green.
Page 8
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
Figure 16.1.5: Thematic Mapping of p-factors at TII TMU Sites
Page 9
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
The mapping shows an influence of geography on the p-factor, and hence on the shape of the traffic
flow profile. There is a pattern of low p-factor values in the northwest and border regions, and to a
lesser extent through the Greater Dublin Area. Higher values are found in the west/southwest
regions.
As a result of the above findings, it is appropriate to develop a range of traffic flow profiles which
reflect the different patterns across the Country, effectively reducing the standard deviation in pfactors within each area and facilitating a more accurate estimation of the 24-hour traffic flow from a
short period traffic count. The following geographic regions have been identified:

Dublin;

Mid-East (Kildare, Meath & Wicklow);

Mid-West (Limerick, Clare & North Tipperary);

Midland (Laois, Longford, Offaly & Westmeath);

South-East (Carlow, Kilkenny, Wexford, South Tipperary & Waterford);

West (Galway, Mayo & Roscommon);

Border – West (Donegal, Sligo & Leitrim);

Border – East (Louth, Monaghan & Cavan);

South-West (Kerry);

South-West (Cork County); and

South-West (Cork City).
The relevant Traffic Flow Profiles for these areas are outlined in Appendix A of this PAG Unit. A
series of examples outlining the conversion of short period traffic counts to 24-hour weekday totals
are provided:
Example 1: Conversion of Short Period Traffic Count to a 24-hour total.
Consider a traffic count covering the period from 08:00 to 09:00 on the N26 between Foxford and
Swinford, Cloongullane, Co. Mayo. The traffic count reports a traffic flow of 268 vehicles per hour (2way).
Step 1:
Step 2:
Step 3:
Identify the relevant geographical location. For this example, the relevant profiles are
for the West.
Identify the proportion of daily traffic flow that relates to the short period count. From
Appendix A it can be seen that the proportion of the 24-hour flow occurring during the
period 08:00 – 09:00 is 0.077.
Perform the calculation. The 24-hour estimate is therefore as follows
268/0.077 = 3,480
The 24-hour estimate is therefore 3,480 vehicles
Page 10
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
Example 2: Conversion of Short Period Traffic Count to a 24-hour total.
Consider a traffic count covering the period from 08:00 to 09:00 and 14:00 – 16:00 on the N11 at
Ferrycarraig, Co Wexford. The traffic count reports a traffic flow of 2,988 vehicles (2-way) during
the combined hours.
Step 1:
Step 2:
Step 3:
Identify the relevant geographical location. For this example, the relevant profiles are
for South East.
Identify the proportion of daily traffic flow that relates to the short period count. From
Appendix A it can be seen that the proportion of the 24-hour flow occurring during the
period 08:00 – 09:00 and 14:00 – 16:00 is 0.225. (This is calculated as the sum of
0.086, 0.067 and 0.072 which cover the three individual time periods.
Perform the calculation. The 24-hour estimate is therefore as follows:
2,988/0.225 = 13,280
The 24-hour estimate is therefore 13,280 vehicles.
Confidence Intervals for expansion factors for each hour to the 24-hour total are also presented in
Appendix A, based on a 95% Confidence Interval. The table shows those values which yield
intervals greater than +20% in grey, suggesting that use of single-hour data from these periods will
not yield a reliable result. For the estimation of 24-hour flow for traffic counts from these periods,
they should be combined with flows from other periods to improve the accuracy of the estimation. In
the case of counts from multiple periods, the 95% Confidence Interval may be assumed as the
lowest value of the various hours for which data is available.
Page 11
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
5.
Factoring by Day of Week
Once a 24-hour estimate is derived, a further calculation can be undertaken to convert this to an
average weekday (or to estimate 24-hour flows that might arise on other weekdays).
Figure 16.1.6 shows a weekly flow profile based on data from the network of TII TMU sites. The data
shows a gradual increase in the 24-hour traffic flow from Monday through to a peak on Friday, with a
reduction in total flows at weekends.
Figure 16.1.6: Weekly Flow Profile
Weekly Flow Profile
1.200
1.000
0.800
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
Sunday
Day of Week Note that Weekly Average Daily Traffic (WADT) refers to the mean 24-hour traffic flow across a
week. This is not to be confused with a Weekday Average, which represents a 24-hour average for
the Monday to Friday period. Geography is not considered to be a significant factor in converting
from a 24-hour estimate to WADT.
A series of Weekly Flow Indices have been generated using this data to enable the conversion from
a specific day to a Weekly Average day. These are outlined in Appendix B of this PAG Unit. An
example of a conversion from a single day to an estimate of the Weekly Average Daily Traffic is
provided in Example 3.
Example 3: Conversion of 24-hour flow to a Weekly Average Day.
Consider a 24-hour traffic volume collected on a Tuesday. The traffic count reports a traffic flow of
12,500 vehicles over the 24-hours.
Step 1:
Identify the relevant day, which in this case is a Tuesday.
Step 2:
Extract the correct factor to convert to Weekday Average Day. For a Tuesday,
Appendix B shows that the relevant factor is 0.99
Step 3:
Perform the calculation. The WADT is therefore as follows:
12,500*0.99 = 12,375
The WADT estimate is therefore 12,375 vehicles.
Page 12
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
6.
Factoring by Month of Year
The final calculation is to convert WADT to AADT. This final stage recognises the significant
variation that can occur in traffic flows across the year. Such variations arise as a result of:

The seasonal effects of tourism/public holidays;

Reductions in school/work trips during holiday periods;

The effect of annual leave on the volume of commuting trips during the summer
months; and

Changes in the level of retail activity.
This effect is also referred to as seasonality, which describes the variability in traffic flow at different
times of the year. To demonstrate the scale of the seasonality effect, Figure 16.1.7 shows WADT for
each month in relation to AADT. The data shows that daily traffic flows peak during the summer
period, with the lowest flows during the months of December and January.
Figure 16.1.7: Monthly Flow Profile
WADT by Month
1.200
Proportion of AADT
1.100
1.000
0.900
0.800
It is noted that the relatively low level of traffic flow during December and January is influenced by
the Christmas period where traffic flows reduce significantly over a period of 2 weeks. This therefore
reduces WADT for that period. Likewise, the high levels of traffic in August are driven by the
increased levels of tourism and leisure movements which tend to take place outside peak periods.
Page 13
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
For the purpose of this PAG Unit, the monthly indices for December and January have been
adjusted to remove the influence of the Christmas Period. In this regard, these relationships do not
hold for short period traffic counts undertaken during periods of abnormal traffic flow (i.e. Christmas,
Easter or Bank Holiday weekends). Furthermore, care should be taken when using short period
traffic counts for July and August to extrapolate to AADT due to the influence of tourist traffic on the
24-hour traffic flow profile. Where possible, some conversion to 24-hour data using the TII TMU sites
or temporary count sites should be considered.
Monthly Flow Indices to account for the influence of seasonality are outlined in Appendix C of this
PAG Unit. An example of a conversion from a single day to an estimate of the Weekly Average Daily
Traffic is provided in Example 4.
Example 4: Conversion of Weekly Average Day to Annual Average Day.
Consider a Weekly Average Daily Traffic Flow of 10,000 vehicles on a site in Co. Roscommon
during March. This is to be converted to an estimate of AADT.
Step 1:
Step 2:
Step 3:
Identify the relevant month, which in this case is March.
Extract the correct factor to convert to Annual Average Day. For the Month of March,
Appendix C shows that the relevant factor is 1.04.
Perform the calculation. The AADT is therefore as follows:
10,000*1.04 = 10,400.
The AADT estimate is therefore 10,400 vehicles.
Page 14
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016
7.
Dealing with Multiple Datasets
In some cases, a selection of data may be available to support the estimation of AADT. For
example, a particular location may provide data for March and a separate dataset for May, and
estimating AADT from these datasets individually will provide different results.
Whilst some variability in the results is expected, it is noted that the procedure outlined in this PAG
Unit is intended to give no more than an indicative estimate of AADT based on short period traffic
counts. Where more detailed estimates are required, reference should be made to PAG Unit 16.0:
Estimating AADT on National Roads.
Where multiple results for a single site can be derived based on alternative data, the user should
take a practical view as to the conclusions that can be inferred from them. Obviously the more data
that is captured within the short period traffic count; the more robust will be the final calculation.
Page 15
Appendix A:
Sample Traffic Flow Profiles
(2015)
Page 16
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
Dublin Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 17
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
Mid East Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 18
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
Mid West Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 19
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
Midland Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 20
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
South‐East Region
0.120
Proportion of Total Daily Flow
0.100
0.080
0.060
0.040
0.020
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 21
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
West Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 22
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
Border (West) Region
0.1
0.09
Proportion of Total Daily Flow
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 23
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
Border (East) Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 24
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
South‐West (Kerry) Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 25
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
South‐West (Cork County) Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Page 26
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Hourly Traffic Flow as a Proportion of 24‐Hour Traffic Flow
South‐West (Cork City) Region
0.100
0.090
Proportion of Total Daily Flow
0.080
0.070
0.060
0.050
0.040
0.030
0.020
0.010
0.000
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
Hour Beginning
Hourly Traffic Flow as a Proportion of 24-hour Traffic Flow
Page 27
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
Region
Hour Ending
06:00
07:00
01:00
02:00
03:00
04:00
05:00
Dublin Region
0.008
0.004
0.003
0.004
0.007
0.013
Mid East
0.006
0.004
0.003
0.003
0.005
Mid West
0.006
0.004
0.003
0.003
Midland
0.006
0.004
0.003
South East
0.005
0.004
West
0.007
Border (West)
PE-PAG-02039
October 2016
08:00
09:00
10:00
11:00
12:00
0.037
0.077
0.081
0.066
0.055
0.055
0.012
0.044
0.071
0.078
0.062
0.053
0.053
0.004
0.008
0.023
0.061
0.084
0.065
0.056
0.057
0.003
0.004
0.009
0.023
0.050
0.077
0.065
0.053
0.055
0.002
0.002
0.003
0.009
0.027
0.060
0.086
0.067
0.058
0.059
0.004
0.003
0.002
0.003
0.008
0.023
0.055
0.077
0.070
0.060
0.063
0.006
0.003
0.002
0.002
0.003
0.005
0.014
0.042
0.073
0.064
0.056
0.060
Border (East)
0.006
0.004
0.003
0.003
0.005
0.012
0.026
0.049
0.078
0.063
0.056
0.059
South-West (Kerry)
0.005
0.003
0.002
0.002
0.002
0.005
0.016
0.040
0.068
0.063
0.062
0.067
South-West (Cork County)
0.005
0.003
0.003
0.003
0.004
0.009
0.027
0.072
0.082
0.064
0.054
0.056
South-West (Cork City)
0.006
0.003
0.003
0.003
0.004
0.009
0.023
0.069
0.082
0.063
0.052
0.053
13:00
14:00
15:00
16:00
17:00
20:00
21:00
22:00
23:00
24:00
Dublin Region
0.059
0.062
0.063
0.069
0.083
0.088
0.075
0.054
0.039
0.031
0.022
0.014
Mid East
0.056
0.058
0.061
0.066
0.080
0.093
0.080
0.053
0.037
0.028
0.019
0.012
Mid West
0.060
0.063
0.064
0.072
0.083
0.093
0.075
0.052
0.038
0.028
0.018
0.011
Midland
0.058
0.060
0.063
0.068
0.076
0.088
0.071
0.049
0.036
0.027
0.018
0.010
South East
0.062
0.065
0.067
0.072
0.082
0.096
0.077
0.050
0.036
0.026
0.017
0.010
West
0.065
0.068
0.070
0.075
0.083
0.095
0.082
0.056
0.040
0.030
0.020
0.013
Border (West)
0.063
0.066
0.068
0.072
0.079
0.088
0.071
0.049
0.037
0.027
0.019
0.011
Border (East)
0.063
0.065
0.067
0.072
0.078
0.091
0.075
0.053
0.038
0.028
0.019
0.011
South-West (Kerry)
0.068
0.068
0.071
0.076
0.083
0.092
0.075
0.049
0.034
0.025
0.017
0.010
South-West (Cork County)
0.059
0.062
0.063
0.069
0.083
0.088
0.075
0.054
0.039
0.031
0.022
0.014
South-West (Cork City)
0.056
0.058
0.061
0.066
0.080
0.093
0.080
0.053
0.037
0.028
0.019
0.012
Region
Hour Ending
18:00
19:00
95% Confidence Intervals for 24-hour Flow Estimations
Page 28
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
Region
Hour Ending
06:00
07:00
01:00
02:00
03:00
04:00
05:00
Dublin Region
11%
4%
3%
6%
17%
26%
Mid East
5%
4%
4%
4%
5%
Mid West
4%
4%
5%
5%
Midland
4%
4%
4%
South East
3%
5%
West
9%
Border (West)
PE-PAG-02039
October 2016
08:00
09:00
10:00
11:00
12:00
31%
47%
38%
21%
15%
17%
11%
35%
35%
29%
18%
12%
12%
4%
8%
20%
53%
49%
16%
16%
19%
5%
5%
10%
24%
38%
67%
48%
36%
37%
4%
4%
4%
9%
25%
31%
44%
14%
8%
10%
3%
4%
5%
5%
10%
32%
57%
64%
53%
37%
44%
5%
4%
4%
4%
4%
8%
17%
46%
69%
44%
40%
43%
Border (East)
6%
5%
4%
5%
7%
16%
41%
33%
55%
20%
11%
13%
South-West (Kerry)
6%
4%
3%
3%
6%
12%
29%
57%
80%
24%
34%
43%
South-West (Cork County)
4%
3%
4%
4%
7%
13%
27%
64%
58%
34%
27%
27%
South-West (Cork City)
10%
6%
6%
6%
17%
32%
44%
110%
145%
93%
74%
73%
13:00
14:00
15:00
16:00
17:00
20:00
21:00
22:00
23:00
24:00
Dublin Region
21%
22%
21%
21%
32%
41%
30%
16%
14%
11%
13%
14%
Mid East
11%
12%
15%
16%
20%
32%
30%
18%
13%
13%
8%
6%
Mid West
22%
24%
18%
17%
23%
36%
19%
12%
10%
8%
8%
5%
Midland
39%
41%
42%
45%
52%
68%
52%
35%
26%
19%
13%
7%
South East
12%
11%
14%
14%
14%
27%
20%
19%
10%
7%
7%
4%
West
44%
50%
52%
59%
65%
75%
69%
50%
41%
33%
20%
14%
Border (West)
45%
44%
45%
46%
53%
59%
48%
31%
25%
18%
14%
8%
Border (East)
15%
20%
17%
15%
20%
29%
21%
15%
11%
8%
5%
5%
South-West (Kerry)
38%
32%
33%
33%
25%
31%
28%
18%
15%
13%
12%
10%
South-West (Cork County)
28%
30%
31%
34%
43%
52%
41%
26%
20%
15%
12%
8%
South-West (Cork City)
80%
84%
85%
92%
117%
140%
110%
71%
54%
41%
32%
21%
Region
Hour Ending
18:00
19:00
Page 29
Appendix B:
Weekly Flow Indices
Page 30
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Daily Traffic Flow as a Proportion of WADT
Monday
Tuesday
Wednesday
Day
Thursday
Friday
Saturday
Sunday
Dublin Region
1.02
1.07
1.09
1.09
1.11
0.85
0.77
Mid East
1.00
1.03
1.05
1.06
1.13
0.89
0.84
Mid West
0.99
0.99
1.02
1.04
1.16
0.91
0.88
Midland
0.99
1.00
1.03
1.04
1.16
0.91
0.88
South East
0.99
1.02
1.04
1.06
1.14
0.90
0.84
West
0.99
1.02
1.04
1.05
1.14
0.92
0.84
Border (West)
0.99
1.00
1.02
1.03
1.14
0.94
0.88
Border (East)
0.99
1.01
1.03
1.04
1.14
0.94
0.85
South-West (Kerry)
0.98
0.99
1.01
1.03
1.12
0.97
0.90
South-West (Cork County)
1.00
1.04
1.07
1.08
1.14
0.87
0.80
Region
1.01
1.07
1.09
1.10
1.13
0.85
0.74
South-West (Cork City)
Note:
Proportion of WADT measures the level of the 24-hour flow for any day against the weekly average day (i.e. traffic flow for a Thursday in the Midland region is
1.04 times the Weekly Average Daily Traffic).
Page 31
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Weekly Flow Indices – Regional Breakdown
Monday
Tuesday
Wednesday
Day
Thursday
Dublin Region
0.98
0.94
0.92
0.92
0.90
1.18
1.29
Mid East
1.00
0.97
0.95
0.94
0.89
1.12
1.19
Mid West
1.01
1.01
0.98
0.96
0.86
1.10
1.14
Midland
1.01
1.00
0.97
0.96
0.86
1.10
1.14
South East
1.01
0.98
0.96
0.95
0.88
1.12
1.19
West
1.01
0.98
0.96
0.95
0.87
1.09
1.19
Border (West)
1.01
1.00
0.98
0.97
0.87
1.06
1.14
Border (East)
1.01
0.99
0.97
0.96
0.87
1.06
1.18
South-West (Kerry)
1.02
1.01
0.99
0.97
0.89
1.03
1.11
South-West (Cork County)
1.00
0.96
0.93
0.93
0.87
1.15
1.26
0.99
0.94
0.92
South-West (Cork City)
Note:
The Index is the factor that is applied to the 24-hour total to convert it to WADT
0.91
0.88
1.18
1.35
Region
Friday
Saturday
Sunday
Page 32
Appendix C:
Monthly Flow Indices
Page 33
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
WADT for each month as a Proportion of AADT
Region
Month
June
July
Jan.
Feb.
March
April
May
Aug.
Sept.
Oct.
Nov.
Dec.
Dublin Region
0.91
0.98
0.98
1.01
1.02
1.03
1.03
1.01
1.04
1.02
0.99
0.97
Mid East
0.88
0.97
0.98
1.03
1.02
1.04
1.06
1.08
0.98
1.01
1.01
0.95
Mid West
0.83
0.93
0.95
1.01
1.04
1.04
1.10
1.11
1.07
1.02
0.97
0.92
Midland
0.86
0.96
0.97
1.02
1.03
1.03
1.06
1.07
1.06
1.02
0.99
0.93
South East
0.87
0.95
West
0.85
0.94
0.97
1.02
1.03
1.03
1.08
1.08
1.04
1.02
0.99
0.93
0.95
1.02
1.03
1.04
1.10
1.11
1.05
1.02
0.97
0.91
Border (West)
0.80
0.93
0.95
1.03
1.04
1.05
1.13
1.16
1.04
1.02
0.95
0.90
Border (East)
0.86
0.97
0.98
1.02
1.02
1.03
1.07
1.07
1.02
1.02
0.99
0.96
South-West (Kerry)
0.76
0.84
0.89
1.02
1.08
1.10
1.24
1.28
1.08
1.00
0.88
0.84
South-West (Cork County)
0.76
0.84
0.89
1.02
1.08
1.10
1.24
1.28
1.08
1.00
0.88
0.84
0.91
0.99
0.99
1.02
1.02
1.02
1.02
1.00
1.04
1.02
1.01
0.96
South-West (Cork City)
Note:
Proportion of AADT measures the level of the WADT for each month against AADT (i.e. WADT in March in the South East region is 0.97 times the AADT).
Page 34
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short Period Traffic Counts
PE-PAG-02039
October 2016
Monthly Flow Indices – Regional Breakdown
Region
Month
June
July
Jan.
Feb.
March
April
May
Aug.
Sept.
Oct.
Nov.
Dec.
Dublin Region
1.10
1.02
1.02
0.99
0.98
0.97
0.97
0.99
0.96
0.98
1.01
1.03
Mid East
1.13
1.03
1.02
0.97
0.98
0.96
0.94
0.93
1.02
0.99
0.99
1.06
Mid West
1.20
1.07
1.05
0.99
0.96
0.96
0.91
0.90
0.94
0.98
1.03
1.09
Midland
1.16
1.05
1.03
0.98
0.97
0.97
0.94
0.93
0.94
0.98
1.01
1.08
South East
1.15
1.05
West
1.18
1.06
1.04
0.98
0.97
0.97
0.93
0.92
0.96
0.98
1.01
1.08
1.05
0.98
0.97
0.96
0.91
0.90
0.95
0.98
1.03
1.09
Border (West)
1.24
1.08
1.05
0.97
0.97
0.95
0.88
0.86
0.96
0.98
1.06
1.11
Border (East)
1.16
1.03
1.02
0.98
0.98
0.97
0.94
0.93
0.98
0.98
1.01
1.05
South-West (Kerry)
1.31
1.19
1.12
0.98
0.93
0.91
0.81
0.78
0.93
1.00
1.14
1.19
South-West (Cork County)
1.31
1.19
1.12
0.98
0.93
0.91
0.81
0.78
0.93
1.00
1.14
1.19
1.09
1.02
1.01
0.98
South-West (Cork City)
Note:
The Index is the factor that is applied to WADT to convert it to AADT.
0.98
0.98
0.98
1.00
0.96
0.98
0.99
1.04
Page 35
TII Publications
Project Appraisal Guidelines for National Roads Unit 16.1 - Expansion Factors for Short
Period Traffic Counts
PE-PAG-02039
October 2016