HCC/1/G
Note on most recent BAA Traffic Forecasts
Impact on A120 at Little Hadham Bypass
Background
1.BAA submitted BAA/3/F, ‘Little Hadham Bypass – 2014 Test with Revised Signal Timings’, on 25 September. This showed new AM peak hour forecast traffic for the 35 mppa Enhanced scenario for roads west of Bishop’s Stortford assuming an increased capacity at Little Hadham on the A120 as a result of changed signalisation timings.
2. As indicated at the Inquiry further details of the model runs and explanations of the changes were requested from BAA following their submission of the new information. (A note of the requests is appended.) To date (16.00 hrs 10 October) no response has been received from BAA so this note has been produced without the benefit of the further details requested.
3.The changes to the traffic forecasts in BAA/3/F are due to the improvements to the traffic signals made as a result of BAA’s contribution as part of the 2003 permission. These changes were implemented in 2004 (as BAA were aware) so it is unclear why they were not included in the original modelling.
4.At the request of HCC, BAA provided forecasts for the 25 mppa case with the improved signals. BAA provided figures for the A120 either side of Little Hadham and for the B1004, with the first set being provided on the 26 September but then withdrawn and replaced.
5.The new figures are shown in Table G1. The total AM peak hour traffic flows forecast are greater than those currently observed (Table D2 HCC/1/D). The highest flows recorded are less than 1400 vehicles two way east of Little Hadham rather than over 1500 as BAA forecast (over 10% higher than recorded).
Issues Arising
6.The issues for the Local Authorities arising from the new forecasts with the assumed increase in capacity at Little Hadham are:
- the increase in airport traffic at 25 and 35 mppa with the improved signalisation, and
- the change in forecast flows on other roads, particularly the B1004.
The greater flows of airport traffic associated with the permitted 25 mppa airport could be considered to reduce the benefit of a Little Hadham Bypass to the airport.
HCC/1/GTABLE G1 Update of Table D1 HCC/1/D with 35m improved signalisation Forecasts
Forecast Flows near Little Hadham
2003 / 2014 25 MPPA Imp Signals / 2014 35 MPPA Imp Signals / Inc 2003 to 35M Imp Signals
AM Peak Hour / Airport / Total / Airport / Total / Airport / Total / Airport / Total
A120 W of LH
Eastbound / 54 / 607 / 86 / 739 / 88 / 741 / 34 / 134
Westbound / 40 / 507 / 65 / 620 / 69 / 620 / 29 / 113
Total / 94 / 1114 / 151 / 1359 / 157 / 1361 / 63 / 247
A120 E of LH
Eastbound / 58 / 752 / 88 / 871 / 89 / 871 / 31 / 119
Westbound / 42 / 581 / 71 / 668 / 75 / 666 / 33 / 85
Total / 100 / 1333 / 159 / 1539 / 164 / 1537 / 64 / 204
Average A120 W & E of LH
Eastbound / 56 / 680 / 87 / 805 / 89 / 806 / 33 / 127
Westbound / 41 / 544 / 68 / 644 / 72 / 643 / 31 / 99
Total / 97 / 1224 / 155 / 1449 / 161 / 1449 / 64 / 226
B1004 MH-BS
Eastbound / 14 / 164 / 37 / 242 / 42 / 242 / 28 / 78
Westbound / 3 / 353 / 7 / 558 / 9 / 567 / 6 / 214
Total / 17 / 517 / 44 / 800 / 51 / 809 / 34 / 292
A10 Wadesmill Bypass
Northbound / 25 / 848 / 18 / 1332 / -7 / 484
Southbound / 22 / 1088 / 16 / 1358 / -6 / 270
Total / 47 / 1936 / 34 / 2690 / -13 / 754
Source BAA/3/F and additional information from BAA (HCC/1/E)
Note: Averages rounded to whole numbers which may affect calculated percentages
7.The change in total AM peak hour traffic either side of Little Hadham as a result of the re-modelled signals is the same for both the 25 and 35 mppa cases, about 300 vehicles. Airport related vehicles however increase by more in the 25 mppa cases (35 on average and westbound east of the lights) than in the 35 mppa cases (30 on average and eastbound east of the lights) (Table G2).
8.The reason that airport related traffic would increase more with a 25 mppa airport than with a 35 mppa one is unclear. The result is airport traffic eastbound (approaching Stansted) in the AM peak is virtually the same for both the 25 and 35 mppa enhanced cases without a bypass. Without the signal improvements and with the bypass the differences were forecast at about 10 vehicles, an increase that was questioned by HCC as being very small.
HCC/1/GTABLE G2 Difference between 25 and 35 mppa Table D1 HCC/1/D and improved signalisation Forecasts Table F1 HCC/1/F
Forecast Flows near Little Hadham
Change 25M to 25M Imp Signals / Change 35M to 35M Imp Signals / Change 25M IS to 35M Imp Signals / Change 25M to 35M TAAU
AM Peak Hour / Airport / Total / Airport / Total / Airport / Total / Airport / Total
A120 W of LH
Eastbound / 27 / 232 / 22 / 226 / 2 / 2 / 7 / 8
Westbound / 5 / 57 / 6 / 54 / 4 / 0 / 3 / 3
Total / 32 / 289 / 28 / 280 / 6 / 2 / 10 / 11
A120 E of LH
Eastbound / 35 / 218 / 30 / 218 / 1 / 0 / 6 / 0
Westbound / 3 / 83 / 2 / 84 / 4 / -2 / 5 / -3
Total / 38 / 301 / 32 / 302 / 5 / -2 / 11 / -3
Average A120 W & E of LH
Eastbound / 31 / 225 / 26 / 222 / 1.5 / 1 / 7 / 4
Westbound / 4 / 70 / 4 / 69 / 4 / -1 / 4 / 0
Total / 35 / 295 / 30 / 291 / 5.5 / 0 / 11 / 4
B1004 MH-BS
Eastbound / -3 / -78 / -5 / -93 / 5 / 0 / 7 / 15
Westbound / 0 / -53 / 0 / -52 / 2 / 9 / 2 / 8
Total / -3 / -131 / -5 / -145 / 7 / 9 / 9 / 23
9.If BAA’s most recent forecast for a 25 mppa airport traffic with improved signalisation is used and compared with the 35 mppa plus 15% with a bypass scenario the proportion of total airport traffic growth (62 vehicles) over total traffic growth (684 vehicles) is 9% (Table G3). Using the original 25 mppa forecasts the figure was 9.9% (97979 HCC/1/D).
10.Greater capacity on the A120 at Little Hadham as modelled by improved signalisation would mean reduced traffic (airport and non-airport) on other roads. Figure 1 of BAA/3/F shows that most of the extra traffic at 35 mppa comes from north of the A120 rather than from the south.
11.18 of the additional 23 airport related vehicles eastbound west of Little Hadham are from the A10 north of the A120 junction. Airport traffic southbound on this stretch of the A10 is forecast at 48 vehicles virtually identical to the level forecast with a bypass at Little Hadham (49 vehicles for 35 mppa Enhanced). 164 of the total additional traffic (226) on the A120 west of Little Hadham could also be assumed to be from the A10 north. (Figure 1 BAA/3/F).
HCC/1/GTABLE G3 Update of Table D7 HCC/1/D with 25M improved signalisation and 35m+15% with LH Bypass Forecasts
Forecast Flows near Little Hadham with Bypass
Growth 25mppa I S without to 35m+15% with Bypass
2014 25 MPPA IS without Bypass / 2014 35M+15% with LH Bypass / Increase 25M IS without to 35M+15%with / % Airport of Total 35M+15% with / %Airport Growth of Total 35M+15% with / %Airport Growth of
Total Growth 35M+15% with
AM Peak Hour / Airport / Total / Airport / Total / Airport / Total
A120 W of LH
Eastbound / 86 / 739 / 120 / 978 / 34 / 239 / 12.3% / 3.5% / 14.2%
Westbound / 65 / 620 / 93 / 1036 / 28 / 416 / 9.0% / 2.7% / 6.7%
Total / 151 / 1359 / 213 / 2014 / 62 / 655 / 10.6% / 3.1% / 9.5%
A120 E of LH
Eastbound / 88 / 871 / 125 / 1139 / 37 / 268 / 11.0% / 3.2% / 13.8%
Westbound / 71 / 668 / 95 / 1112 / 24 / 444 / 8.5% / 2.2% / 5.4%
Total / 159 / 1539 / 220 / 2251 / 61 / 712 / 9.8% / 2.7% / 8.6%
Average A120 W & E of LH
Eastbound / 87 / 805 / 123 / 1059 / 36 / 254 / 11.6% / 3.4% / 14.0%
Westbound / 68 / 644 / 94 / 1074 / 26 / 430 / 8.8% / 2.4% / 6.0%
Total / 155 / 1449 / 217 / 2133 / 62 / 684 / 10.2% / 2.9% / 9.0%
B1004 MH-BS
Eastbound / 37 / 242 / 23 / 130 / -14 / -112 / 17.7% / -10.8% / 12.5%
Westbound / 7 / 558 / 6 / 342 / -1 / -216 / 1.8% / -0.3% / 0.5%
Total / 44 / 800 / 29 / 472 / -15 / -328 / 6.1% / -3.2% / 4.6%
Source: Figures from BAA additional to TAAU HCC/1/E and Fig 6.1 BAA/3/E
Note: Averages rounded to whole numbers which may affect calculated percentages
A10 25M without bypass figures are those for 35M with improved signals
12.Most surprising is that there is no change in airport traffic and a small decrease in traffic travelling north on the A10 Wadesmill Bypass south of the A120. However with the bypass at Little Hadham airport traffic on this road increases markedly (18 to 40 vehicles 35 mppa Enhanced, Table G4). It would be expected that airport traffic would therefore increase with the improved signalisation with vehicles using the B1004 from Ware to Bishop’s Stortford diverting to the A10/A120 but this is not the case.
13.The BAA forecasts do show 5 fewer airport related vehicles and 93 fewer total vehicles travelling eastbound on the B1004east of Much Hadham as a result of the improved signalisation. If these vehicles re-route to the A120 it is unclear how they get there.
HCC/1/GTABLE G4 Change in Forecast Flows on A10
TAAU / Improved Signals / With LH Bypass
2014 25 MPPA without Bypass / 2014 35 MPPA without Bypass / 2014 35 MPPA IS without Bypass / 2014 35M with LH Bypass
AM Peak Hour / Airport / Total / Airport / Total / Airport / Total / Airport / Total
A10 N Standon-Buntingford
Northbound / 26 / 1085 / 30 / 1089 / 32 / 1102 / 34 / 1146
Southbound / 24 / 1381 / 30 / 1390 / 48 / 1474 / 49 / 1491
Total / 50 / 2466 / 60 / 2479 / 80 / 2576 / 83 / 2637
A10 Wadesmill Bypass
Northbound / 18 / 1346 / 18 / 1343 / 18 / 1332 / 40 / 1404
Southbound / 18 / 1340 / 16 / 1437 / 16 / 1358 / 24 / 1569
Total / 36 / 2686 / 34 / 2780 / 34 / 2690 / 64 / 2973
Source BAA/3/F and TAAU
14.BAA have that suggested some could divert from the A602 (from Stevenage) onto the B158 and the old A10 at Wadesmill. This though would suggest that previously the vehicles were modelled as continuing on the A602 into Ware, through Ware High Street and out onto the B1004. The AM peak delays on this route would be likely to be equal to those at Little Hadham so such a change is unlikely.
Conclusions
15.The modelled forecasts and the routes shown are very complicated with net changes which make any direct comparisons of different scenarios difficult. Nevertheless the new forecasts provided by BAA only serve to add to the uncertainties regarding airport traffic and the difference between the 25 mppa and 35 mppa developments and regarding the implications of the capacity constraint that exists at Little Hadham.
16.A new bypass at Little Hadham is considered by HCC to be essential to meet existing traffic problems which will only be exacerbated by further growth at Stansted. Airport users of the A120 west, those existing, those presently deterred by the congestion and those created by future development, will all benefit from a bypass as will those villages on those roads presently used as alternative routes. The new forecasts suggest no reason for HCC to change its request for a contribution to a Little Hadham Bypass from BAA equivalent to about 10% of the cost.
Appendix : Information requested from BAA
Explanatory Note 3 Oct 2007
Queries emerging from Ian Forshew’s evidence as requested by Counsel
1.Further Detail on the ‘Improved signalisation’ Traffic Forecasts produced by BAA week of 25 September
2014 forecasts were provided for 35mppa without the bypass.
The query was regarding changes in flow south of the A120
how the traffic diverting from the B1004 reaches the A120
why there is no increase on the A10 north
The suggested answer was that traffic on the A602 was using Anchor Lane (B158) and the old A10 road. It is unclear given the congestion on the A602 into Ware and on Ware High Street why even with the old signalisation this traffic would go this way.
Not raised by Counsel because the final figures were presented after the event but there is a question over the comparison between the Imp Sig 25 and 35 mppa airport traffic at Little Hadham. The difference is even less than with the original forecasts.
What are the reasons for this.
2.Traffic forecasts for Bishops Stortford with the LH Bypass
Aspects of BAA/3/G & L have not yet been resolved as regards potential changes in flow on the BS Bypass
Where is the additional traffic into BS arising – changes in flows
Where does the 88 fewer vehicles shown as not emerging from the Tesco roundabout on the A1184 actually go. If it is not an actual reduction would they use the BS Bypass or other routes.
3.24 hour or late night/early morning STEX services
Ian Forshew was asked as to the likelihood/commitment to 24 hour or extended STEX services.
(This question has been dealt with separately)