public inquiry documentbailey.persona-pi.com/public-inquiries/m4-newport/e - pi... ·...

M4 Corridor around Newport

PUBLIC INQUIRY DOCUMENT

REFERENCE NO. : ID/065

RAISED BY: Mr Bryan Whittaker DATE: 22/05/17

RESPONDED BY: ‐ DATE: ‐

SUBJECT: Publication of Statistical Article: Vehicle speeds for Welsh motorways, April to June 2016

The data that informed the statistical article was provided from in-vehicle global positioning systems GPS), in which the GPS signal omits its location every ten seconds, which are used to calculate journey times for each vehicle journey. The same source of data was used that informed the evidence to the Public Local Inquiry. The statistical article recognises that the analysis undertaken and the methodology applied in respect of vehicle speeds on Welsh Motorways, differs from that used in the M4 Corridor around Newport Public Local Inquiry.

The differences which can be summarised as follows;

▪ the analysis in the Welsh Government Publication uses data from the two years to June 2016 in respect of vehicle speeds on Welsh motorways.

▪ average speeds were produced by Welsh Government in respect of the 07.00 -10.00 and 16.00 – 19.00 time periods for the M4 in specific in the Newport Local Authority. The derivation of vehicle speeds by Local Authority used a subset of the data referred to above for April to June 2016. In the evidence submitted to the Public Local Inquiry average speeds were produced using data from September to October 2015 by 15 minute time periods between 6.00 and 10.00.

▪ In respect of the M4 in the Newport Local Authority, the length of motorway considered was that from J23a to J29 and is consistent with the length of motorway considered in the presentation of evidence to the Public Inquiry. However in the evidence presented to the Public Local Inquiry, average speeds were presented by 15 minute time periods between J23a and J29 broken down into individual sections of motorway between junctions and comprised of 7 individual sections of M4. The analysis therefore that is presented in evidence to the Public Local Inquiry is therefore at a greater level of disaggregation.

▪ vehicle speeds for cars only are presented in the statistical article presented by Welsh Government, whilst average speeds are presented in the Public Inquiry evidence are based on cars and light goods vehicles and therefore the sample rate was much higher.

▪ Outliers were extracted from the data that informed the Public Local Inquiry. In this respect speeds in excess of 85 mph were removed.

Welsh Government have released data for the M4 as a whole between Junction 22 and West of Junction 48. Additionally, they have released data for the length of M4 with the

Newport Local Authority Area which should be a good basis for monitoring transport policy and infrastructure development in Wales and providing a general picture of congestion on Welsh motorways. It is recognised however that the Welsh Government analysis has been carried out over longer sections of motorway than has been used in evidence at the Public Local Inquiry and for longer time periods. It therefore does not show the level of congestion on smaller sections on the M4 which gets overshadowed in the averages by those sections of M4 that are not experiencing congestion.

In conclusion whilst the analysis and the presentation of data in the evidence to the Public Local Inquiry gives a detailed overview of the areas surrounding the M4 Corridor around Newport, the Welsh Government article gives a rounded picture of all motorways in Wales.

Rydym yn croesawu derbyn gohebiaeth yn Gymraeg. Byddwn yn ateb gohebiaeth a dderbynnir yn Gymraeg yn Gymraeg ac ni fydd

gohebu yn Gymraeg yn arwain at oedi.

We welcome receiving correspondence in Welsh. Any correspondence received in Welsh will be answered in Welsh and corresponding

in Welsh will not lead to a delay in responding.

Parc Cathays ● Cathays Park

Caerdydd ● Cardiff

CF10 3NQ

Ffôn ● Tel 0300 025 6691 [email protected]

[email protected] Gwefan ● website: www.llyw.cymru

www.gov.wales

16 May 2017 Dear Sir/ Madam,

I am writing to inform you of the publication of the statistical article ‘Vehicle speeds for Welsh

motorways, April to June 2016’, at 09:30 on the statistics and research area on the Welsh

Government website. These statistics have been produced in accordance with the Code of Practice

for Official Statistics.

This article presents average speed statistics for the M4, M48, and A48 (M); and includes analysis

over time in addition to averages of road traffic speeds by local authority.

The statistical article has been produced following requests for official congestion statistics for

Welsh roads, similar to those produced by the Department for Transport and Scottish Government.

Average road traffic speed is one of the measures for road traffic congestion.

The dataset used for this analysis has also been used in the evidence presented as part of the

inquiry, however there are differences in methodology and presentation of the analysis. The article

provides detailed information on the methodology used.

If you have any comments or queries please feel free to contact me using the details below.

Kind regards, Glyn Jones

Welsh Government Chief Statistician

mailto:[email protected]

mailto:[email protected]

http://www.llyw.cymru/

http://www.gov.wales/

http://gov.wales/statistics-and-research/about/user-engagement/plans-practices/knowledge-analytical-services-evidence-plan/?lang=en

http://gov.wales/statistics-and-research/about/user-engagement/plans-practices/knowledge-analytical-services-evidence-plan/?lang=en

https://www.statisticsauthority.gov.uk/monitoring-and-assessment/code-of-practice/

https://www.statisticsauthority.gov.uk/monitoring-and-assessment/code-of-practice/

Statistician: Craiger Solomons 0300 025 6960 [email protected] Also available in Welsh

Enquiries from the press: 0300 025 8099 Public enquiries : 0300 025 5050 Twitter: @statisticswales

Vehicle speeds on Welsh motorways, April to June 201617 May 2017

This statistical article provides information on vehicle

speeds on Welsh motorways, that is the A48(M), M4

and the M48. This is the first statistical publication of

motorway speeds in Wales.

The data for this article is taken from in-vehicle global

positioning systems (GPS). The data are collected for

navigation or stolen vehicle tracking services purposes.

The methodology for developing this analysis has been developed in

conjunction with the Department for Transport (DfT). However these

estimates are not the same as the DfT estimates of road traffic congestion for

the English Strategic Road Network, nor Scottish Government’s estimates of

road traffic congestion for Scottish motorways.

Due to the differences in methodology, notably weighting the sampled

observations using annual traffic volume data, aggregated values of roads

are not presented in this article. Further information on this can be found in

the key quality Information.

Key points

The M4 and the M48 were at their slowest westbound at the evening

peak and at their fastest eastbound during non peak times. The A48(M)

was at its slowest eastbound during the evening peak and fastest during

the non-peak times westbound.

From April to June 2014 to April to June 2016, vehicle speeds have

generally decreased across all three Welsh motorways, although this

may be due to other extraneous factors such as sampling changes,

weather or the number of road accidents.

For the A48(M) and the M4, vehicle speeds are slower in the morning

peak during schooldays.

In general the M4 is at it’s fastest through Bridgend.

The M4 is generally at its slowest westbound in the morning peak

through Neath Port Talbot and in the evening peak both ways through

Newport and westbound in Monmouthshire and Neath Port Talbot.

About this article

This article provides

estimates of road traffic

speeds on Welsh

motorways.

The continuation and/or

expansion of this product is

dependent on user feedback.

We welcome all feedback on

any aspect of these statistics

which can be provided by via

the contact information

below.

In this article

1. Key points …………p1

2. Context………...…...p2

3. Methods used..……p3

4. Type of vehicle........p4

5. Direction of travel....p5

6. Time series..............p6

7. School days……....p12

8. Area on the M4…..p13

9. Time of day…..…..p15

10. Key quality

Information............p18

1. Context

These statistics have been developed following user feedback which requested official statistics on

average speeds for Welsh motorways.

Potential uses of these statistics include:

monitoring transport policy and infrastructure development in Wales;

providing a picture of congestion on Welsh motorways; and

investigating the impact of road accidents on motorways in Wales.

The analysis included in this article focus on indicators which could be used to measure road traffic

congestion. Road traffic congestion is defined as overcrowding of vehicles on a road. Congestion on

roads has been shown to have a negative impact on both the environment and the economy. Vehicles

travelling at a reduced speed for longer periods of time are likely to cause additional pollution. Delays in

journey times mean that the volume of business and personal travel is reduced, leading to less goods

and services provided as well as commuting to and from employment. Of course there are additional

costs too, with a high volume of congestion our emergency services find it difficult to carry out their

functions effectively.

Road traffic congestion can be measured in a variety ways, for example: traffic moving at a lower speed

than expected, increased journey times, and/or unreliable journeys times; this article focuses on the

average vehicle speed of road traffic. Other measures, such as average delay, journey reliability and the

impact of road accidents are also important factors when trying to fully understand a road as a whole.

The focus of this article is on motorways in Wales only.

As the sampled data have not been weighted to the estimated road traffic flows, individual roads and

vehicles types are specified throughout this article. This means that aggregations should not be

calculated (to combine different roads or sections of roads) as the difference in the sampled

observations does not allow simple averaging.

There are three motorways in Wales; these are the A48 (M), M4 and the M48. The map below shows the

coverage of each road used in this analysis. The M4 in Wales runs from Carmarthenshire through 8 local

authorities and finishes at the end of the Second Severn Crossing at junction 22. The A48 (M) and the

M48 branch off the M4. The A48 (M) connects Cardiff and Newport, whilst the M48 branches off the M4

at Monmouthshire and allows an alternative route than using the toll bridge.

2. Methods used in this article

The figures below outline how the data were collected and analysed for this article, further information can be found in the key quality section.

2. Vehicle speeds by type of vehicle

This section analyses the difference in vehicle speeds between cars and Light Good Vehicles (LGVs).

Buses and taxis were excluded due to the stop start nature of these vehicles. Heavy Goods Vehicles

(HGVs) were also excluded due to their speed restrictions on certain roads.

Table 1 shows vehicle speeds for Cars and LGVs, for April to June 2016 across all times of the day. The

largest difference in vehicle speeds between vehicle types are observed on the A48(M) at 65.9 miles per

hour (mph) for cars and 63.9 mph for LGVs, a difference of 2.0 mph. Vehicle speeds on the M4 were 1.9

mph slower for LGVs than cars (using unrounded data). On the M48, vehicle speeds were the same for

both Cars and LGVs, at 56.2 mph.

The total volume of motorised traffic on all Welsh motorways for 2015 was estimated to be 76.8 per cent

for cars and taxis compared to 14.3 per cent for light vans1. Any subsequent analysis in this release

refers to cars only, unless otherwise stated.

Table 1: Vehicle speeds (mph) by vehicle type and road name, April to June 2016

Miles per hour

Cars LGVs Difference

A48(M) 65.9 63.9 2.0

M4 66.1 64.3 1.8

M48 56.2 56.2 0.0

Source - Statistics for Wales, Welsh Government

1 Source: http://gov.wales/docs/statistics/2016/161130-road-traffic-2015-en.pdf

3. Vehicle speeds by time period and direction of travel

This section highlights the difference in vehicle speeds by direction of travel, during the morning and

evening peak travel times for cars, for April to June 2016.

The M4 and the M48 were at their slowest westbound at the evening peak and at their fastest eastbound

during non peak times. The A48 (M) was at its slowest eastbound during the evening peak at and fastest

during the non-peak times westbound.

Vehicle speeds on the A48 (M) ranged from the slowest of 52.8 mph eastbound during the

evening peak to 68.4 mph westbound during non-peak times. During the evening peak and

non peak times, speeds on the westbound road were quicker than the eastbound.

The M4 was at its slowest westbound during the evening peak at 56.6 mph and at it’s

fastest, eastbound during non peak times, at 68.0 mph. For the morning peak, speeds

travelling westbound were faster than travelling eastbound

The M48 was slowest westbound during the evening peak at 44.1 mph. The eastbound

during non peak times were the fastest, at 63.0 mph. For all three time periods, travelling

eastbound was quicker than travelling westbound.

The M48 and M4 westbound were generally slower than the other roads. These roads include sections

where there are tolls (Severn River Crossing) which require vehicles to stop. This will reduce the

average speed of the road.

Table 2: Vehicle speeds (mph) on Welsh motorways for cars by time period and direction, April to

June 2016, for cars only.

Miles per hour

Eastbound Westbound Eastbound Westbound Eastbound Westbound

A48(M) 63.3 59.5 52.8 67.9 68.0 68.4

M4 65 66.8 65.4 57 68.1 66.6

M48 60.4 53.7 61.2 44.1 63.0 50.7Source - Statistics for Wales, Welsh Government

Evening Peak (16:00‐19:00)Morning Peak (07:00‐10:00) Non‐Peak Times

4. A time series of quarterly vehicle speeds

This section investigates the change in vehicle speeds for cars on the A48 (M), M4 and the M48 by

quarter. Please note that the charts in this section start at 35 mph (rather than 0 mph).

From April to June 2014 to April to June 2016, vehicle speeds have generally decreased across all three

Welsh motorways, although, this may be due to other extraneous factors such as sampling changes,

weather and the number of road accidents.

4.1 A48(M)

Chart 1 highlights that average vehicle speeds have become more variable during the

morning peak period (07:00-10:00) over the time. Comparing April to June 2014 and April

to June 2016, vehicle speeds during the morning peak travelling eastbound increased by

0.8 mph, compared to a decrease of 2.0 mph travelling westbound. The change in April to

June 2016 from a year earlier shows a decrease of 1.4 mph eastbound and a 2.5 mph

increase travelling westbound.

Chart 1 - Vehicle speeds (mph) during the morning peak on the A48(M) by direction, cars

only

35

40

45

50

55

60

65

70

Apr-Jun 14 Jul-Sep 14 Oct-Dec 14 Jan-Mar 15 Apr-Jun 15 Jul-Sep 15 Oct-Dec 15 Jan-Mar 16 Apr-Jun 16

Ave

rage

Speed (mph)

Quarter

Eastbound

Westbound


Between April to June 2014 and April to June 2016 vehicle speeds during the evening peak

time on the A48 (M), decreased by 13.6 mph travelling eastbound, and increased by 1.8 mph

travelling westbound. From a year ago, vehicle speeds during the evening peak time show a

decrease of 5.4 mph eastbound and a 0.2 mph increase westbound (chart 2).

2014 2016

Chart 2 - Vehicle speeds (mph) during the evening peak on the A48(M) by direction, cars only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound


Comparing April to June 2014 and April to June 2016, vehicle speeds across non peak

times travelling eastbound decreased by 0.9 mph. Similarly vehicle speeds travelling

westbound also decreased, down 1.1 mph, over the same time frame. Vehicle speeds

increased travelling eastbound when comparing April to June 2015 to the same quarter in

2016, up 0.5 mph. The vehicle speeds travelling westbound increased by 0.6 mph (chart 3)

Chart 3 - Vehicle speeds (mph) during non peak times on the A48 (M) by direction, cars

only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound


4.2 M4

During the morning peak in April to June 2016, vehicle speeds on the M4 eastbound were

down 1.2 mph from April to June 2014 and down 1.1 mph compared to April to June 2015.

There was an increase in speed on the M4 westbound from April to June 2014, at 0.3 mph,

and an increase of 0.5 mph from April to June 2015. Chart 4 highlights the similarity in

vehicle speeds in both directions (chart 4).

Chart 4 - Vehicle speeds (mph) during the morning peak on the M4 by direction, cars only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound


During the evening peak, vehicle speeds on the M4 decreased when comparing April to

June 2016 to the same quarter in 2014 and 2015. There was a decrease of 2.3 mph travelling

eastbound from the same quarter in 2014 and a decrease of 0.7 mph from the same quarter

in 2015. Vehicle speeds westbound decreased by 2.9 mph from the same quarter in 2014

and down 3.1 mph over the same quarter in 2015 (chart 5).

Chart 5 - Vehicle speeds (mph) during the evening peak on the M4 by direction, cars only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound


Comparing April to June 2014 and April to June 2016, vehicle speeds across non peak

times on the M4 decreased, down 1.2 mph eastbound and down 0.1 mph westbound.

Vehicle speeds fell when compared the same quarter in 2015, down 0.1 mph eastbound and

down 0.2 mph westbound (chart 6).

Chart 6 - Vehicle speeds (mph) during non peak times on the M4 by direction, cars only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound


4.3 M48

During the morning peak (07:00-10:00) vehicle speeds travelling eastbound fell by 7.0

mph from two years ago and 6.3 mph a year ago. Vehicle speeds increased travelling

westbound from two years ago by 1.1 mph. Although in the latest year, vehicle speeds

have decreased by 1.5 mph (chart 7).

Chart 7 - Vehicle speeds (mph) during the morning peak on the M48 by direction, cars only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound


The westbound evening peak (16:00-19:00) had the largest change in vehicle speeds, down

10.8 mph on the year and down 8.5 mph from two years ago. This compares to a fall of 6.4

mph travelling eastbound from one year ago and a fall of 6.3 mph two years ago (chart 8).

Chart 8 - Vehicle speeds (mph) during the evening peak on the M48 by direction, cars only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound

Source - Statistics for Wales, Welsh Government Across non peak times, vehicle speeds travelling westbound and eastbound fell when

comparing April June 2016 to the same quarter in 2014, down 2.8mph eastbound and down

1.1 mph westbound. The change over the same time period from 2015 also shows a

reduction in vehicle speeds, down 3.4 mph eastbound and down 1.5 mph westbound (chart

9).

Chart 9 - Vehicle speeds (mph) during non peak times on the M48 by direction, cars only

35

40

45

50

55

60

65

70


Ave

rag

e S

pe

ed

(mp

h)

Quarter

Eastbound

Westbound


5. Vehicle speeds during school days and non-school days

This section highlights the difference in vehicle speeds for cars, during school days and non-school

days, for April to June 2016. School days are defined as week days during term time, non-school days

are defined as all days during non-term time and weekends during term time. School terms vary between

local authorities in Wales. We were not able to take INSET days into account as they can differ within

local authorities.

For the A48 (M) and the M4, vehicle speeds are slower in the morning peak during schooldays than

for non-school days. This results for differences of 13.3 mph eastbound on the A48 (M) and 15.7 mph

westbound. Similarly, there were differences of 7.9 mph and 4.7 mph between vehicle speeds during

school days and non-school days, eastbound and westbound on the M4. This is also true in the

evening peak, other than for the M4 eastbound, although this differs by 0.1 mph.

For the M48 vehicle speeds eastbound are higher during non-school days (0.8 mph) during the

morning peak, compared to higher westbound speeds during school days. The reverse results are

observed during the evening peak, school days are quickest eastbound and non-school days are

quickest westbound.

In general there is very little difference in non-peak times between school days and non-school days.

Table 3: Vehicle speeds (mph) on Welsh motorways by school day and non-school dayMiles per hour

Schoolday School Holiday Schoolday School Holiday Schoolday School Holiday

Eastbound 55.1 68.4 50.8 53.7 69.0 67.4

Westbound 50.2 65.9 66.4 68.6 68.3 68.5

Eastbound 60 67.9 65.5 65.4 68.6 67.8

Westbound 64.1 68.2 53.3 59 66.8 66.5

Eastbound 59.9 60.7 64.6 59.7 63.8 62.6

Westbound 58.1 51.7 40.3 46.3 49.7 51.3


M48

M4

A48(M)

Morning Peak (07:00-10:00) Evening Peak (16:00-19:00) Non Peak times

6. Vehicle speeds on the M4 by direction of travel, travel time and local authority

This section looks at vehicle speeds for cars on the M4 (in Wales) by local authority, for April to June

2016. Only the M4 is analysed here as the M48 (within Wales) is only located in Monmouthshire and the

A48 (M) covers Cardiff and Newport only. The M4 spans across nine different local authorities in Wales.

The analysis looks at the difference in speeds across times of day. Annex A outlines which junctions are

within each local authority.

In general the M4 is at it’s fastest through Bridgend and then at different times of the day, the Vale of

Glamorgan, Cardiff and Rhondda Cynon Taff. It is at its slowest westbound in the morning through Neath

Port Talbot, and in the evening both ways through Newport and westbound in Monmouthshire and Neath

Port Talbot. Speeds in Neath Port Talbot, Monmouthshire and Newport are affected by the fixed speed

limit zones, the Severn Bridge tolls and the enforcement of the variable speed limits, respectively.

Looking at the morning peak time (between 07:00-10:00), Bridgend westbound had the highest average

speed at 73.9 mph. The lowest vehicle speed during the morning peak was in Neath Port Talbot

westbound at 58.2 mph, although this would be influenced by the 50 mph speed limit within certain

sections of the local authority (chart 10).

Chart 10 - Vehicle speeds (mph) on the M4 by local authority and direction during the morning

peak, for cars during April to June 2016

64.2

68.7

61.3

73.9

73.2

70.9

71.9

61.0

63.3

67.6

64.8

62.2

71.6

58.9

70.7

68.1

70.6

61.5

66.8 65.0

80 60 40 20 0 20 40 60 80

Carmarthenshire

Swansea

Neath Port Talbot

Bridgend

Vale of Glamorgan

Cardiff

Rhondda Cynon Taf

Monmouthshire

Newport

Average Speed (mph)

Lo

cal

Au

tho

riti

es

on

th

e M

4

Westbound Eastbound

Westbound Average Eastbound Average


The highest vehicle speeds during the evening peak were travelling eastbound in Bridgend; at 74.2 mph.

Monmouthshire westbound had the slowest observed vehicle speeds during the evening peak, at 36.9

mph, 36.0 mph below the vehicle speeds travelling eastbound. This is likely to be due to the impact of

having to slow down at the toll (included in the analysis). Other than Monmouthshire, vehicle speeds

were also low travelling westbound in Newport at 47.7 mph. Although vehicle speeds in Monmouthshire

were lower than Newport, the total distance of the M4 in Newport is much greater, at 47.4km compared

to 25.4km covered in Monmouthshire respectively (chart 11).

Chart 11 - Vehicle speeds (mph) on the M4 by local authority and direction during the evening

peak, for cars during April to June 2016

67.4

66.4

61.8

74.2

71.7

67.3

73.3

72.8

58.1

62.0

67.5

51.4

73.2

71.4

68.0

71.5

36.9

47.7

65.457.0

80 60 40 20 0 20 40 60 80

Carmarthenshire

Swansea

Neath Port Talbot

Bridgend

Vale of Glamorgan

Cardiff

Rhondda Cynon Taf

Monmouthshire

Newport

Average Speed (mph)

Lo

cal

Au

tho

riti

es

on

th

e M

4

Westbound Eastbound

Westbound Average Eastbound Average


The Vale of Glamorgan westbound had the highest average speed across the remainder of the day on

the M4 in Wales, at 74.2mph. The slowest average speed were observed travelling westbound in

Monmouthshire at 56.1 mph, followed by Neath Port Talbot westbound at 59.1 mph. Vehicle speeds

within Monmouthshire are influenced by the M4 toll road, where vehicles are required stop. This is

highlighted as the average speed eastbound is 14.6 mph quicker at 70.7 mph.

Table 4 investigates the change in vehicle speeds between April to June 2015 and April to June 2016. A

reduction in average speed could suggest that these roads are becoming more congested. It’s also

important to note that other factors could have affected vehicle speeds during this time period i.e. road

works, change in speed limits, weather, sampling and others.

Vehicle speeds travelling eastbound in Rhondda Cynon Taff had the highest decrease, down 4.0 mph

between April to June 2015 and April to June 2016, during the morning peak. This was followed by

travelling eastbound in Newport down 3.3 mph. Carmarthenshire eastbound had the highest speed

increase, up 2.1 mph, in these time periods.

During the evening peak, the largest change in speed was observed travelling westbound in

Monmouthshire, down 16.4 mph; again this may be affected by the number of vehicle observations on

the M4 toll, which only occurs travelling westbound. The second largest change in average speed was

travelling eastbound in Cardiff, down 3.3 mph. Vehicle speeds increased in 3 local authorities, eastbound

in Swansea (up 3.2 mph), westbound in Neath Port Talbot (up 0.5 mph) and eastbound in

Monmouthshire (up 0.3 mph).

Non peak times varied across local authorities ranging from an increase of 1.7 mph travelling westbound

in Carmarthenshire to a decrease of 4.3 mph travelling westbound in Monmouthshire.

Table 4: Change in vehicle speeds (mph) on the M4 by time period, direction of travel and local

authority for cars, between April to June 2015 and April to June 2016

Change in miles per hour

Eastbound Westbound Eastbound Westbound Eastbound Westbound

Carmarthenshire 2.1 -0.4 -0.7 -0.1 -0.7 1.7

Swansea 1.5 0.6 3.2 -1.0 -1.1 -1.1

Neath Port Talbot -0.9 0.6 -0.2 -0.6 1.4 0.6

Bridgend -1.6 1.1 -0.6 -0.3 0.2 1.5

Vale of Glamorgan 0.8 0.3 -1.2 -0.8 1.5 1.1

Cardiff 1.1 1.1 -3.3 -1.2 -0.2 0.3

Rhondda Cynon Taf -4.0 -0.3 -0.6 -0.9 1.0 0.7

Monmouthshire -1.1 -1.9 0.3 -16.4 -0.8 -4.3

Newport -3.3 1.1 -1.9 -2.6 -1.6 0.1


Morning Peak (07:00-10:00) Evening Peak (16:00-19:00) Remainder of the day

7. Vehicle speeds by time of day

This section examines vehicle speeds for cars on the three Welsh motorways by each 15 minute interval

throughout each day. The beginning of the 15 minute interval is labelled below, for example: 00:00 labels

from 00:00 to 00:14:59. Speeds are only presented where there were at least 50 observations during the

interval in our sample to ensure sufficient quality in the estimates.

7.1 A48(M)

Vehicle speeds by time of day on the A48 (M) are only available from 06:00, due to a low number of

observations at times when road traffic volume is lowest (chart 12).

Vehicle speeds eastbound average at just over 71 mph between 06:00 and 07:00. Vehicle speeds

travelling eastbound then drops overall to a morning low of 57 mph for 07:45 to 08:00. This is most likely

due to the effect of the morning commuter traffic. Speed then varies within the morning peak period, then

increase to 70 mph around 09:30. Average speeds then remain relatively stable at 70 mph, until a dip

around midday. Speeds then increase to just less than 70 mph, before a period of fluctuation between

14:00 and 15:45. From 15:45 the average speed decreases, to just less than 40 mph for 16:00 to 16:15.

The average speed then remains below 65 mph until 18:30. After 18:30 the average speed increases

overall to 74 mph between 20:15 and 20:30.

The westbound speeds on the A48 (M) are above 60 mph between 06:00 to 07:000. Vehicle speeds

then drop to just over 53 mph for 08:45 to 09:00 and remains relativity low until 09:45. Unlike travelling

eastbound, there is no major dip in the average speed travelling westbound after 09:45. The data ranges

from 58.6 mph at 10:15 to 10:30 to a maximum of 72.1 mph between 20:15 to 20:30.

Chart 12 - Vehicle speeds on the A48(M) by time of day and direction, April to June 2016

35

40

45

50

55

60

65

70

75

6_0 6_30 7_0 7_30 8_0 8_30 9_0 9_30 10_0 10_30 11_0 11_30 12_0 12_30 13_0 13_30 14_0 14_30 15_0 15_30 16_0 16_30 17_0 17_30 18_0 18_30 19_0 19_30 20_0

Av

era

ge

Sp

ee

d (

mp

h)

Time of day

Eastbound

Westbound


7.2 M4

The average speed on the M4 eastbound is close to and above 70 mph between 00:00 and 06:45.

From 6:45, the average speed drops, to a daily low of just under 62 mph for 7:30 to 7:45. The average

speed then gradually increases to above 69 mph for 9:30 to 9:45. The average speed then, ranges from

64.2 mph between 12:15 and 12:30 to 73.6 mph between 21:30 and 21:45 (chart 13).

The average speed westbound decreases overall between 00:00 and 07:15, just under 2mph. Between

07:15 to 08:15 the average speed declines. The average speed then decreases slightly overall to 59.7

mph between 15:30 and 15:45. From 15:45 the average speed declines further. Between 17:15 to 17:30

the average speed is at its lowest during the quarter at 51.7 mph. The average speed gradually

increases to 61.8 mph between 18:30 to 18:45pm. Due to the heightened traffic volume anticipated at

this time of day, the vehicle speeds may be affected by the enforcement of the variable limit, although no

data is available to confirm this. The average speed then increases to 69.4 mph between 20:30 and

20:45. For the remaining timeframe vehicle speeds stay fairly constant ranging from 67.8 mph between

21:30 and 21:45 to 72.6 mph between 23:00 and 23:15.

The average speed travelling westbound is lower than travelling eastbound from 9:15am to 20:45. This is

especially evident between 15:30 and 19:15, with a difference of 13.7 mph between both directions at

17:30 to 17:45.

Chart 13 - Vehicle speeds on the M4 by time of day and direction for cars, April to June 2016

35

40

45

50

55

60

65

70

75

80

85

0_0 1_0 2_0 3_0 4_0 5_0 6_0 7_0 8_0 9_0 10_0 11_0 12_0 13_0 14_0 15_0 16_0 17_0 18_0 19_0 20_0 21_0 22_0 23_0

Ave

rag

e S

pe

ed

(mp

h)

Time of day

Eastbound

Westbound


8.3 - M48

The M48 is presented from 07:00 to between 20:15 and 20:30, due to the low sample size. The data

shows the volatility of the average speed for this road compared to the previous two. Travelling

eastbound the average speed ranges from a minimum of 51.8 mph during 07:45 and 08:00 to 71.4 mph

between 19:30 and 19:45. As chart 14 shows the westbound speed is considerably lower than the

average speed travelling eastbound, with the maximum difference of 26.3 mph between 08:45 to 9:00.

The average speed travelling westbound is quite volatile from 07:00 to between 09:15 and 09:30. From

09:30 to 09:45 the average speed starts to become more stable, at 50.3 mph and is unchanged overall

when compared to the average speed between 15:30 to 15:45. From 15:45, the average speeds

decreases by 11.5 mph between 16:15 and 16:30, to 38.8 mph. The average speed then steadily

increases for the remainder of the day (Chart 14).

Chart 14 - Vehicle speeds for the M48 by time of day and direction for cars, April to June 2016

35

40

45

50

55

60

65

70

75

7_0 7_30 8_0 8_30 9_0 9_30 10_0 10_30 11_0 11_30 12_0 12_30 13_0 13_30 14_0 14_30 15_0 15_30 16_0 16_30 17_0 17_30 18_0 18_30 19_0 19_30 20_0

Ave

rag

e S

pe

ed

(m

ph

)

Time of day

Eastbound

Westbound


Key quality information

Relevance

This release provides an estimate on vehicle speed on Welsh motorways. These statistics will be used to

monitor speeds on motorways in Wales.

These statistics could be used by a variety of organisations within and outside the Welsh Government to

assess the transportation needs for Wales. Key users are expected to be:

Ministers and the Members research Service in the National Assembly for Wales;

Interested parties in the M4 Corridor Around Newport Public Local Inquiry

Welsh Government transport policy teams;

Trunk Road Agents;

Businesses

Academia;

Local Authorities;

Students; and

the media.

Users are encouraged to provide feedback on how these statistics have been published, presented and

how well they meet users’ needs. Comments on any issues relating to this statistical release are

welcomed and encouraged. Contact information is outlined in the ‘We want your feedback’ section

below.

Accuracy

In this statistical article estimates are only presented where there are 50 observations. This is deemed

suitable robust for the production of these statistics.

The data are compiled from a sample of observations from TrafficMaster GPS data. The data are

collected through GPS and mobile communications functionality fitted in vehicles, for Fleet Tracking,

Stolen Vehicle Tracking and Satellite Navigation purposes. This information is sent in an anonymised

form to the Welsh Government. This information is then linked to the Integrated Transport Network (ITN)

to calculate an average speed for each section of the road. This data is obtained from administrative

sources and thus may be affected by changes in procedures within those systems.

The statistics presented in this release do not take into consideration other factors that could have

influenced the data such as road works/diversions, weather, accidents or localised events

Table 5 below displays that across all three Welsh motorways, the number of observations of cars are

lower than for LGVs, this reflects how the data is collected. The data are collected from inbuilt satellite

navigation or having stolen vehicle tracking services activated within their vehicle. LGVs are more likely

to have this technology activated in their vehicles; therefore the number of observations is much larger

for LGVs. However, as LGVs have additional speed restrictions on motorways they have typically been

excluded from analysis presented in this article.

Table 5: The number of observations by type of vehicle and road name, April to June 2016(1)

Number

Cars LGVs Difference

A48(M) 30,500 115,300 -84,800

M4 1,491,700 7,570,200 -6,078,500

M48 32,400 91,900 -59,500


(1) This includes duplicated vehicles

Timeliness and punctuality

The Welsh Government receives the Welsh subset of data from DFT every two months, for use in this

analysis. The most recent data was submitted to the Welsh Government and covers the period up to

August 2016. The frequency of future updates to this analysis will be decided on depending user

responses to our upcoming consultation.

Accessibility and clarity

This release and headline are available on the Welsh Governments Statistical website.

Definitions

See annex C on the area of the A48(M), M4, M48 used in this article.

Morning peak time is the time between 07:00 to 10:00.

Evening peak time is the time between 16:00 to 19:00.

Non peak times, excludes the morning and evening peak time (00:00 to 07:00 and 10:00 to

16:00 and 19:00 to 00:00).

Comparability and coherence

The Welsh average speed estimates are not comparable to the methodology used by DFT to calculate

travel time measures for England. Scotland publish travel time data using the Scotland’s Intelligent

Transport Systems (ITS), due to this methodological difference it is not directly comparable to this

release. Northern Ireland do not currently publish any travel time statistics. See links for further

information:

England: www.gov.uk/government/collections/road-congestion-and-reliability-statistics

Scotland: www.transport.gov.scot/road/technology-and-traffic-scotland

It should be noted the road structures in Wales differ to that of England, Scotland and Northern Ireland.

Any comparisons between countries and local authorities should take into consideration the different

road types, lengths, locations and speed restrictions. The individual named roads within Wales should

also not be compared, as the flow of traffic on each one differs in quantity.

The analysis in this article differs from that used in the M4 Corridor Around Newport Public Local Inquiry.

For example, in the public enquiry evidence the vehicle speeds are presented by junctions whilst this

article does not. Annex A provides a junction to local authority lookup for reference. Also, the public

enquiry evidence includes vehicle speeds for both cars and LGVs.

Well-being of Future Generations Act (WFG)

The Well-being of Future Generations Act 2015 is about improving the social, economic, environmental

and cultural well-being of Wales. The Act puts in place seven well-being goals for Wales. These are for a

more equal, prosperous, resilient, healthier and globally responsible Wales, with cohesive communities

and a vibrant culture and thriving Welsh language. Under section (10)(1) of the Act, the Welsh Ministers

must (a) publish indicators (“national indicators”) that must be applied for the purpose of measuring

progress towards the achievement of the Well-being goals, and (b) lay a copy of the national indicators

before the National Assembly. The 46 national indicators were laid in March 2016.

Information on indicators and associated technical information - How do you measure a nation’s

progress? - National Indicators

Further information on the Well-being of Future Generations (Wales) Act 2015.

The statistics included in this release could also provide supporting narrative to the national indicators

and be used by public services boards in relation to their local well-being assessments and local well-

being plans.

Notes on the use of statistical articles

Statistical articles generally relate to one-off analyses for which there are no updates planned, at least in

the short-term, and serve to make such analyses available to a wider audience than might otherwise be

the case. They are mainly used to publish analyses that are exploratory in some way, for example:

Introducing a new experimental series of data;

A partial analysis of an issue which provides a useful starting point for further research but that

nevertheless is a useful analysis in its own right;

Drawing attention to research undertaken by other organisations, either commissioned by the Welsh

Government or otherwise, where it is useful to highlight the conclusions, or to build further upon the

research;

An analysis where the results may not be of as high quality as those in our routine statistical releases

and bulletins, but where meaningful conclusions can still be drawn from the results.

Where quality is an issue, this may arise in one or more of the following ways:

being unable to accurately specify the timeframe used (as can be the case when using an

administrative source);

the quality of the data source or data used; or

other specified reasons.

However, the level of quality will be such that it does not significantly impact upon the conclusions. For

example, the exact timeframe may not be central to the conclusions that can be drawn, or it is the order

of magnitude of the results, rather than the exact results, that are of interest to the audience.

The analysis presented does not constitute a National Statistic, but may be based on National Statistics

outputs and will nevertheless have been subject to careful consideration and detailed checking before

publication. An assessment of the strengths and weaknesses in the analysis will be included in the

article, for example comparisons with other sources, along with guidance on how the analysis might be

used, and a description of the methodology applied.

Articles are subject to the release practices as defined by the release practices protocol, and so, for

example, are published on a pre-announced date in the same way as other statistical outputs.

Missing value symbols used in the article follow the standards used in other statistical outputs, as

outlined below.

Further details

The document is available at: http://gov.wales/statistics-and-research/vehicle-speeds-welsh-

motorways/?lang=en

Next update

We are currently reviewing our outputs and the continuation of this product is dependent on our user

feedback.

We want your feedback

We welcome any feedback on any aspect of these statistics which can be provided by email to

[email protected].

Open Government Licence

All content is available under the Open Government Licence v3.0, except where otherwise stated.

.. The data item is not available

. The data item is not applicable

- The data item is not exactly zero, but estimated as zero or less than half the final digit

shown

* The data item is disclosive or not sufficiently robust for publication

Annex A – List of junctions and road lengths, by local authority

LACode RoadName Junction

Percentage of the road length in LA

Monmouthshire M4 J23A-J23 100%

Monmouthshire M4 J23A-J24 10%

New port M4 J23A-J24 90%

Monmouthshire M4 J23-J22 100%

Monmouthshire M4 J23-J23A 100%

Monmouthshire M4 J24-J23A 8%

New port M4 J24-J23A 92%



New port M4 J25-J24 100%








Cardiff M4 J29-J30 10%








The Vale of Glamorgan M4 J33-J32 6%




Rhondda Cynon Taff M4 J34-J35 91%


Bridgend M4 J35-J34 6%








Neath Port Talbot M4 J37-J38 37%













Sw ansea M4 J44-J43 22%








Carmarthenshire M4 J48-J47 9%


Carmarthenshire M4 J48-JEnd 100%

Carmarthenshire M4 JEnd -J48 100%

Annex B – Quality assurance undertaken on the data

Each vehicle collects its position (from GPS) data every 10 seconds when the ignition is ‘on’ and the

data is downloaded (via GPRS) to their servers. Prior to receiving the data the following steps are taken

to clean the data:

1) Filter out low quality GPS data - This removes the GPS data that is deemed either physical

impossible (e.g. an impossibly high speed or acceleration) or self-contradictory (e.g. speed/

direction travelled does not agree with change in position).

2) Interpolate at 1-second intervals – The data are then interpolated to 1-second intervals. This

ensures that the GPS data feed into subsequent phases are consistent 1-second frequency,

making it much easier to test and ensure correctness.

3) Correct GPS-shift errors - This stage initially maps the GPS location to closest road by

triangulating the direction travelled. .

4) Final map-matching phase - This phase map-matches the filtered, interpolated and corrected

GPS data using a "restricted and weighted routing algorithm", as follows:

a) Draw a time-gap-dependent buffer around the GPS data.

b) Identify the road segments that lie within the buffer.

c) Assign a weight to each road segment depending on how well the position and direction of the

GPS matches the road segment geometry.

d) Identify the "clear-winner" GPS points. These are the points that are a very good match for

precisely one road segment and a poor match for all other road segments.

e) Use Dijkstra's algorithm to calculate the optimal route from the first to last clear-winner GPS

point using the weighted road speeds.

f) The algorithm allows illegal manoeuvres, but legal routes are favoured to give the driver the

benefit of the doubt in ambiguous cases.

g) Snap the GPS data to the closest point on the calculated optimal route.

h) Check that the snapped GPS data is both spatially and temporally consistent with the

calculated optimal route.

i) If there are any inconsistencies, use a binary chop algorithm to split the GPS into sections that

can be map-matched consistently.

j) Note that each section can have one or more unmatched (i.e. off-network) GPS points at the

start and end of the journey.

k) Insisting on beginning and ending at a clear winner prevents from falsely matching off-network

driving (e.g. driving in car parks) at the start and end of the journey.

Annex C – Map of the motorways in Wales

public inquiry documentbailey.persona-pi.com/public-inquiries/m4-newport/e - pi... ·...

Documents