Hutt Valley – Porirua Link Option Assessment Wellington Transport Strategy Model Analysis

4 Strategic Modelling Forecasts – Base

This section describes the conditions of travel in the regional generally and between Porirua and the Hutt Valley in particular. Its purpose is to present a rationale for the network interventions described in Section 2.

It achieves this by documenting model forecasts for the base 2006 to 2026 scenarios using the assumptions described in Section 3. It provides a summary of changes in demand pressures and network performance both at an aggregate level and at key locations. Those network performance measures are listed below:

• Trip distribution change;

• Traffic flows at key locations around the Hutt Valley to Porirua Corridor;

• Volume capacity analysis both at an aggregate and localised level; and

• Travel times between town centres in Porirua and Lower Hutt.

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4.1 Trip Demand and Distribution Changes

This section reports modelled two hour sector to sector demand changes between 2006 and 2026. It shows:

• How trip distribution is forecast to change under base forecast scenario assumptions. For example, increasing highway congestion and travel times can cause some people to reduce the distances they are prepared to travel; and

• The overall level of demand for travel for the main areas in questions: Hutt Valley and Porirua. Trips to and from Wellington have also been added due to the influence it has on commuter traffic from Porirua and the Hutt Valley.

Heavy Commercial Vehicles (HCV) and car trips have been added together in the following three tables (Table 4-1, Table 4-2, and Table 4-3) presenting sector to sector movements across the AM, IP, and PM Peak base models between 2006 and 2026. The results are summarised below:

• Table 4-1 shows a 23% overall increase in trips between 2006 and 2026 in the AM Peak. In terms of key movements relevant to this study, the largest growth in sector to sector demand is from Wellington to both Porirua and Lower Hutt –28% and 30% respectively. There is no growth in demand in trips from Lower Hutt to Porirua while trips from Porirua to Lower Hutt only grow by 8%. This is likely to be a function of low growth in population in Lower Hutt and Porirua and connections that have reached capacity (Ngauranga Interchange and SH58).

• Table 4-2 shows a 23% overall increase in trips between 2006 and 2026 in the IP Peak. In terms of key movements relevant to this study, the largest growth in sector to sector demand is from Wellington to both Porirua and Lower Hutt (+23%). Trips between Porirua and Lower Hutt (both directions) are forecast to grow by between 10% and 9% respectively. Trips to Wellington from Lower Hutt and Porirua are forecast to rise by between 18% and 20% respectively.

• Table 4-3 shows a 20% overall increase in trips between 2006 and 2026 in the PM Peak. In terms of key movements relevant to this study, the largest growth in sector to sector demand is from Lower Hutt to Wellington (+22%). Trips from Porirua to Lower Hutt are forecast to decrease by 2% and trips from Lower Hutt to Porirua are forecast to increase by 7%. Trips to Wellington from Lower Hutt and Porirua are forecast to rise by between 22% and 23% respectively.

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While the pattern of traffic remains focussed on Wellington one of the more interesting conclusions to draw from the above analysis is the forecast growth in both Porirua and Lower Hutt as key attractors, with some of the largest increases being:

• Trips going from Wellington to Lower Hutt and Porirua in the AM Peak;

• Trips going from Porirua and Lower Hutt to Wellington in the PM Peak (ie return trips); and

• Trips between Lower Hutt and Kapiti also show some high growth rates and these are some of the trips that can switch from the current SH1/SH2 and SH2/SH58 corridors to the new Petone-Grenada Link.

• As employment has been assumed to grow significantly faster than population in Porirua and Lower Hutt some of these new workers will need to travel from areas where there is greater population growth. Modelling undertaken in this study indicates that a significant portion of them could come from Wellington (one of the fast growing population centres).

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Table 4-1 : AM Change in Vehicle Trip Distribution 2006-2026

AM 2006

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South UpperHutt Wellington Total Grand Carterton 1,352 53 8 24 669 7 241 41 48 2,442 External 41 - 991 52 351 87 9 25 143 1,700 Kapiti 12 923 12,274 312 16 664 14 150 1,060 15,425 Lower Hutt 59 35 191 25,309 85 810 63 1,466 6,079 34,097 Masterton 425 235 8 31 8,067 7 168 58 72 9,070 Porirua 20 55 502 1,042 28 10,173 20 414 3,802 16,058 South Wairarapa 415 34 17 74 578 19 1,475 119 112 2,843 Upper Hutt 128 25 118 1,841 191 428 138 8,507 1,487 12,862 Wellington 45 50 399 4,266 81 2,392 62 687 63,189 71,170 Grand Total 2,498 1,411 14,507 32,951 10,065 14,586 2,190 11,468 75,992 165,668 AM 2026

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South UpperHutt Wellington Total Grand Carterton 1,562 52 13 36 785 11 266 61 60 2,846 External 43 - 1,208 75 435 107 9 34 140 2,051 Kapiti 25 1,177 15,804 504 35 927 22 243 1,263 20,000 Lower Hutt 96 48 243 29,685 148 811 93 1,770 6,441 39,335 Masterton 483 268 14 59 9,117 14 226 108 111 10,399 Porirua 33 62 587 1,121 49 12,636 28 474 4,153 19,143 South Wairarapa 441 37 24 76 778 18 1,785 139 106 3,403 Upper Hutt 212 29 126 2,046 338 404 205 10,206 1,396 14,962 Wellington 72 64 483 5,549 136 3,070 82 841 80,687 90,983 Grand Total 2,965 1,736 18,502 39,152 11,821 17,997 2,716 13,877 94,357 203,123 AM % Difference 2006 - 2026

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South Hutt Upper Wellington Total Grand Carterton 16% -2% 69% 47% 17% 47% 11% 50% 26% 17% External 3% 0% 22% 45% 24% 23% -4% 36% -2% 21% Kapiti 100% 28% 29% 61% 117% 40% 60% 63% 19% 30% Lower Hutt 61% 37% 28% 17% 74% 0% 47% 21% 6% 15% Masterton 14% 14% 91% 91% 13% 105% 34% 85% 55% 15% Porirua 60% 12% 17% 8% 74% 24% 41% 14% 9% 19% South Wairarapa 6% 9% 37% 3% 35% -9% 21% 16% -5% 20% Upper Hutt 66% 14% 7% 11% 77% -5% 48% 20% -6% 16% Wellington 60% 26% 21% 30% 68% 28% 32% 22% 28% 28% Grand Total 19% 23% 28% 19% 17% 23% 24% 21% 24% 23%

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Table 4-2 : IP Change in Vehicle Trip Distribution 2006-2026

IP 2006

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South Hutt Upper Wellington Total Grand Carterton 1,247 25 4 26 549 8 305 56 29 2,249 External 27 - 785 27 224 47 11 14 46 1,180 Kapiti 4 783 13,593 180 5 484 7 111 441 15,605 Lower Hutt 27 28 189 25,250 46 668 51 1,347 3,309 30,916 Masterton 554 209 7 45 8,340 13 339 109 66 9,682 Porirua 8 46 535 669 13 10,697 13 327 1,933 14,242 South Wairarapa 307 11 8 50 337 13 1,504 112 49 2,391 Upper Hutt 57 15 118 1,341 107 333 111 9,035 687 11,804 Wellington 30 47 420 3,293 70 1,860 49 641 60,130 66,539 Grand Total 2,261 1,164 15,658 30,882 9,691 14,122 2,388 11,751 66,691 154,607 IP 2026

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South Hutt Upper Wellington Total Grand Carterton 1,480 26 9 51 651 17 337 105 50 2,725 External 28 - 991 42 279 60 11 18 56 1,482 Kapiti 7 987 17,696 229 13 527 10 122 499 20,088 Lower Hutt 53 43 243 29,351 108 726 81 1,566 3,894 36,064 Masterton 659 251 15 108 9,507 34 430 240 120 11,363 Porirua 18 57 613 734 34 13,046 21 360 2,329 17,212 South Wairarapa 337 10 12 80 425 21 1,838 179 70 2,972 Upper Hutt 105 19 132 1,558 232 364 175 10,746 729 14,059 Wellington 53 60 479 4,041 126 2,279 73 705 75,736 83,552 Grand Total 2,740 1,451 20,190 36,193 11,374 17,073 2,976 14,041 83,480 189,518 IP % Difference 2006 - 2026

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South Hutt Upper Wellington Total Grand Carterton 19% 1% 103% 97% 19% 113% 11% 87% 72% 21% External 4% 0% 26% 54% 25% 28% -3% 30% 20% 26% Kapiti 111% 26% 30% 28% 148% 9% 52% 10% 13% 29% Lower Hutt 96% 52% 28% 16% 133% 9% 61% 16% 18% 17% Masterton 19% 20% 130% 138% 14% 165% 27% 120% 80% 17% Porirua 113% 23% 15% 10% 160% 22% 68% 10% 20% 21% South Wairarapa 10% -5% 52% 61% 26% 65% 22% 60% 42% 24% Upper Hutt 83% 28% 12% 16% 116% 9% 58% 19% 6% 19% Wellington 77% 28% 14% 23% 81% 23% 49% 10% 26% 26% Grand Total 21% 25% 29% 17% 17% 21% 25% 19% 25% 23%

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Table 4-3: PM Change in Vehicle Trip Distribution 2006-2026

PM 2006

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South Hutt Upper Wellington Total Grand Carterton 1,610 39 8 52 518 16 400 113 37 2,793 External 39 - 1,058 35 248 60 27 26 49 1,540 Kapiti 3 1,111 15,770 213 4 629 8 153 547 18,438 Lower Hutt 28 48 297 30,584 41 999 60 1,843 4,846 38,746 Masterton 747 328 11 82 9,767 24 584 195 79 11,818 Porirua 8 81 693 849 11 12,954 16 454 2,838 17,904 South Wairarapa 287 13 9 62 268 18 1,819 145 51 2,673 Upper Hutt 54 27 161 1,646 89 450 116 10,930 932 14,406 Wellington 33 123 953 6,064 69 3,625 70 1,435 73,440 85,812 Grand Total 2,809 1,771 18,960 39,589 11,015 18,775 3,100 15,292 82,819 194,130 PM 2026

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South Hutt Upper Wellington Total Grand Carterton 1,840 40 17 93 580 30 407 198 65 3,270 External 40 - 1,323 48 299 68 29 29 56 1,890 Kapiti 7 1,342 20,008 222 11 626 10 136 591 22,951 Lower Hutt 54 68 431 35,105 96 1,071 79 2,035 5,894 44,831 Masterton 838 399 27 166 10,942 51 694 378 140 13,635 Porirua 17 94 878 831 28 15,596 21 446 3,498 21,408 South Wairarapa 297 12 15 105 316 30 2,146 237 75 3,233 Upper Hutt 94 34 215 1,933 188 507 157 12,608 1,036 16,772 Wellington 54 127 1,113 6,488 120 4,098 79 1,381 92,286 105,746 Grand Total 3,241 2,115 24,027 44,989 12,580 22,076 3,621 17,447 103,640 233,736 PM % Difference 2006 - 2026

Row Labels Carterton External Kapiti Hutt Lower Masterton Porirua Wairarapa South Hutt Upper Wellington Total Grand Carterton 14% 2% 120% 79% 12% 85% 2% 75% 76% 17% External 2% 0% 25% 35% 21% 13% 6% 14% 16% 23% Kapiti 118% 21% 27% 4% 173% 0% 33% -11% 8% 24% Lower Hutt 92% 42% 45% 15% 133% 7% 32% 10% 22% 16% Masterton 12% 22% 141% 101% 12% 113% 19% 94% 76% 15% Porirua 109% 15% 27% -2% 166% 20% 34% -2% 23% 20% South Wairarapa 3% -7% 66% 68% 18% 70% 18% 64% 47% 21% Upper Hutt 75% 27% 34% 17% 110% 13% 35% 15% 11% 16% Wellington 64% 3% 17% 7% 73% 13% 13% -4% 26% 23% Grand Total 15% 19% 27% 14% 14% 18% 17% 14% 25% 20%

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4.2 Traffic Flows

This section reports two hour modelled vehicle flow growth between 2006 and 2026 in and around the Hutt Valley-Porirua area. The analysis focuses on traffic counts (HCV and car) in locations illustrated in Figure 4-1.

9 2 10

1

3 4

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7 8 6

Copyright © 1995 -2011 Esri

Figure 4-1 : Count Locations

Table 4-4 shows changes in modelled traffic counts between the 2006 Base Model and the 2026 Base Model. :

• In the AM Peak the largest percentage increase is experienced on SH58 in the Eastbound direction (+40%). This is followed closely by SH2 just south of SH58 which experiences an increase of 34% Northbound. SH1 through Porirua experiences decrease of between 10% and 25% over 2006 levels which is presumed to be an impact of the opening of Transmission Gully route.

• In the Inter Peak the largest percentage increases are again on the SH58 with a 33% increase in flows in both directions. There are again decreases in flows on SH1 just south of Pauatahanui Inlet through Porirua of between 6% and 13%.

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• In the PM Peak the largest percentage change in flows is on SH58 with increases of between 19% eastbound and 39% westbound. Once again, there are decreases in flows on SH1 just south of Pauatahanui Inlet through Porirua of between of between 17% and 18%.

Table 4-4: Base 2026 and Base 2026 Modelled Traffic Counts (HCV + Cars, 2hrs)

AM 2006 AM 2026 inode jnode No. Description Base base % Diff AM Peak 1 SH58 Westbound 7879 1100 1,432 1,653 15% 2 SH58 Eastbound 1100 7879 1,579 2,216 40% 3 SH2 South of SH58 Northbound 1152 7849 2,043 2,736 34% 4 SH2 South of SH58 Southbound 7849 1152 3,461 3,825 11% 5 SH2 South of Petone Northbound 7820 3204 5,584 7,005 25% 6 SH2 South of Petone Southbound 3204 7820 7,975 8,157 2% 7 SH1 North of Ngauranga Interchange Northbound 7585 7583 3,671 3,874 6% 8 SH1 North of Ngauranga Interchange Southbound 7584 7586 9,017 9,829 9% 9 SH1 South of Pauatahanui Inlet Northbound 7762 7766 2,216 2,001 -10% 10 SH1 South of Pauatahanui Inlet Southbound 2766 2762 5,344 4,032 -25% Inter Peak 1 SH58 Westbound 7879 1100 971 1,291 33% 2 SH58 Eastbound 1100 7879 957 1,276 33% 3 SH2 South of SH58 Northbound 1152 7849 1,889 2,314 22% 4 SH2 South of SH58 Southbound 7849 1152 1,907 2,239 17% 5 SH2 South of Petone Northbound 7820 3204 4,466 5,292 18% 6 SH2 South of Petone Southbound 3204 7820 4,529 5,158 14% 7 SH1 North of Ngauranga Interchange Northbound 7585 7583 4,013 4,447 11% 8 SH1 North of Ngauranga Interchange Southbound 7584 7586 4,193 4,709 12% 9 SH1 South of Pauatahanui Inlet Northbound 7762 7766 2,549 2,404 -6% 10 SH1 South of Pauatahanui Inlet Southbound 2766 2762 2,523 2,201 -13% PM Peak 1 SH58 Westbound 7879 1100 1,502 2,081 39% 2 SH58 Eastbound 1100 7879 1,533 1,830 19% 3 SH2 South of SH58 Northbound 1152 7849 3,182 3,654 15% 4 SH2 South of SH58 Southbound 7849 1152 2,360 2,762 17% 5 SH2 South of Petone Northbound 7820 3204 7,854 8,046 2% 6 SH2 South of Petone Southbound 3204 7820 6,432 7,528 17% 7 SH1 North of Ngauranga Interchange Northbound 7585 7583 8,524 9,569 12% 8 SH1 North of Ngauranga Interchange Southbound 7584 7586 4,669 5,048 8% 9 SH1 South of Pauatahanui Inlet Northbound 7762 7766 5,284 4,408 -17% 10 SH1 South of Pauatahanui Inlet Southbound 2766 2762 2,730 2,248 -18%

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One of key factors in determining which locations are forecast to experience the most traffic growth is capacity. For example, the Ngauranga interchange (count site 7 and 8) experience very little growth between 2006 and 2026 because it is already at capacity in peak hours in 2006 while SH58 is forecast to experience up to 40% because it has additional capacity available until 2026.

The concept and application of the highway Volume Capacity relationship is described in more detail in the next section.

4.3 Highway Volume Capacity Analysis

One of the key concerns described in previous studies, and referred to in Section 1.2 of this report, is that traffic growth between Hutt Valley and Porirua along SH58 is expected to reach capacity in the peak hours by 2026. This can be demonstrated more clearly by using Volume / Capacity Ratios (VCR) in combination with Vehicle Kilometres Travelled (VKT).

Vehicle kilometres is simply an aggregate measure of the total distance in km’s travelled by all vehicles in question (in this case both cars and Heavy Commercial Vehicles). VKT is a widely used international proxy for the pressures of road transport on the environment and human health.

The volume capacity ratio (VCR) can be boiled down to the simple relationship between demand and supply i.e. the more demand and the less supply there is, the more congestion there is. In traffic terms, the demand is represented by the number of vehicles that seek to use an asset over a certain interval, while supply is the represented by the number of vehicles that it is possible to use the asset over the same time interval §.

While this concept can be applied to different parts of a network, such as turning movements, intersections, links, pedestrian flows or public transport crowding, this particular section focuses on highway links. Highway links were selected as they can be easily represented on maps and this provides a fast way for the reader to link the concept with what they see in reality.

To further assist the reader in understanding what is meant by different levels of VCR, Table 4-5 below has been extracted from the Highway Capacity Manual. It describes the conditions that might be experienced by highway users under different VCR conditions.

§ In this report the time interval is dictated by the model period which is 2hrs in each of the AM, IP and PM periods. For more detailed descriptions of how volume and capacity have been defined in the model please read the model validation report.

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Table 4-5: Matching Level of Service against Volume Capacity Ratios

GWRC Model LOS Highway Capacity Manual Description VCR Definition

LOS A LOS A describes free-flows operations. 0.00-0.20

LOS B represents reasonably free flow, and free flow speeds are maintained. The ability to manoeuvre within traffic is only LOS B 0.20-0.40 slightly restricted and general level of physical and psychological comfort provided to drivers is still high.

LOS C provides for flow with speeds at or near free flow speed of the road. Freedom to manoeuvre within the traffic stream is LOS C 0.40-0.60 noticeably restricted, and lane changes require more care and vigilance on the part of the driver.

LOS D is the level at which speeds begin to decline slightly. Freedom to manoeuvre within the traffic steam is noticeably LOS D 0.60-0.80 limited, and the driver experiences reduced physical and psychological comfort levels

LOS E describes operational capacity. Operations at this level are volatile because there are virtually no usable gaps in the LOS E 0.80-1.00 traffic stream. Vehicles are closely spaced leaving little room to manoeuvre within the traffic stream.

LOS F Describes total flow breakdown in vehicular flow. Such conditions generally exist within queues forming behind breakdown points. LOS F From a demand modelling perspective this happens at points of >1.00 recurring congestion, where network segments such as merge or weaving segments and lane drops, experience very high demand in which the number of vehicles arriving is greater than the number of vehicles being discharged.

In order to gain an appreciation of how individual trips are affected a graph has been produced that shows the percentage of kms travelled under different VCR conditions.

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100.0% 90.0% 80.0% 70.0% 60.0% 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% Base 2006 Base 2026 Base 2006 Base 2026 Base 2006 Base 2026 AM IP PM VKT with VC Ratio >100% 3.2% 3.3% 0.0% 0.0% 2.6% 3.0% VKT with VC Ratio 80%-100% 11.1% 19.4% 1.6% 7.3% 10.5% 16.7% VKT with VC Ratio 60%-80% 23.5% 19.6% 3.4% 22.1% 21.8% 23.1% VKT with VC Ratio 40%-60% 27.6% 21.4% 31.6% 28.7% 30.1% 24.7% VKT with VC Ratio 20%-40% 24.8% 26.3% 47.7% 35.5% 26.3% 23.4% VKT with VC Ratio 0%-20% 9.9% 10.0% 15.6% 6.4% 8.7% 9.1%

Figure 4-2: % VKT affected by each VCR level (all roads, all vehicles)

Figure 4-2 shows that, despite interventions described in Section 3, individual journeys are forecast to experience an increase in congestion between 2006 and 2026:

• In the AM peak period an average vehicle journey experiencing a VCR of 60% or more increases from 37% to 42% of a total journey;

• In the inter peak period an average vehicle journey experiencing a VCR of 60% or more increases from 5% to 29% of a total journey; and

• In the PM peak period an average vehicle journey experiencing a VCR of 60% or more increases from 35% to 42% of a total journey.

The following graph combines both VKT and VCR to provide an indication of the amount of VKT across the network that is operating at a VCR of 60% to 80%, 80% to 100% and over 100%.

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800,000

700,000

600,000

500,000

400,000

300,000

200,000

100,000

- Base 2006 Base 2026 Base 2006 Base 2026 Base 2006 Base 2026 AM IP PM VKT with VC Ratio >100% 43,604 53,309 327 4,023 37,300 50,462 VKT with VC Ratio 80%-100% 149,042 315,766 16,478 22,752 151,121 282,849 VKT with VC Ratio 60%-80% 316,417 319,141 34,223 127,859 313,035 390,654

Figure 4-3: VKT by Volume Capacity Forecasts (all roads, all vehicles)

Figure 4-3 shows considerable changes in levels of congestion experienced by drivers:

• In the AM peak period total VKT experiencing a VCR of 60% or more increases by 35% between 2006 and 2026;

• In the inter peak period total VKT experiencing a VCR of 60% or more, while very low compared to the other two peaks, increases by 203% between 2006 and 2026; and

• In the PM peak period total VKT experiencing a VCR of 60% or more is subjected to the largest absolute change, increasing by 44% between 2006 and 2026.

To give an indication of where these changes are taking place the following two graphs plot the VCRs on the WTSM network. While the inter-peak demonstrates a significant increase in congestion this is based on a lower congestion level in 2006 and so is not considered excessive, however, the main area of focus are AM and PM peak periods.

Figure 4-4 and Figure 4-5 shows volume capacity ratios for the AM Peak period in 2006 and 2026 respectively. Clearly one of the most congested parts of the AM network in 2006 are Southbound flows along SH1 and SH2 just before Ngauranga Interchange. SH58 is just starting to become congested with a VCR of 0.66 in the eastbound direction. However, by 2026 VCRs are forecast to increase in several key locations:

• Southbound on SH1 north of Ngauranga Interchange which increases from 1.00 to 1.09;

• Northbound on SH2 north of Ngauranga Interchange which increases from 0.73 to 0.92; and

• Eastbound on SH58 increases from 0.66 to 0.92 in 2026.

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Figure 4-6 and Figure 4-7 show volume capacity ratios for the PM Peak period in 2006 and 2026 respectively. One of the most congested parts of the network in 2006 is the northbound direction on SH2 north of Ngauranga Interchange which is modelled as being at over capacity with a VCR of 103% whilst the southbound direction is approaching its capacity at 85%. Northbound flows to the south of Ngauranga Interchange on SH1 are at capacity with VCRs of 0.98. VCRs in both directions on SH58 are modelled at between 0.63 and 0.64. However, by 2026 VCRs are forecast to increase in several key locations:

• Northbound on SH1 north of Ngauranga Interchange which increases from 0.79 to 0.89;

• Southbound on SH2 north of Ngauranga Interchange increases from 0.85 to 0.99; and

• Westbound on SH58 increases from 0.63 to 0.87.

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Figure 4-4 : 2006 AM Peak Period Base Volume Capacity Ratios

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Figure 4-5 : 2026 AM Peak Period Base Forecast Volume Capacity Ratios

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Figure 4-6 : 2006 PM Peak Period Base Forecast Volume Capacity Ratios

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Figure 4-7 : 2026 PM Peak Period Base Forecast Volume Capacity Ratios

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4.4 Highway Travel Times and Average Journey Speeds

The previous section discussed how increased demand affected congestion and VCRs. This section reports how increased congestion is expected to feed through into vehicle travel times.

The focus is on modelled two hour average journey time changes between 2006 and 2026. With Porirua and Lower Hutt being the origin and destination most likely to use any link between Petone and Grenada Table 4-6 lists travel times between them using different routes:

• The Blue Route westbound follows SH2 southbound from Lower Hutt Centre before turning north onto SH1 northbound at Ngauranga Interchange then to Porirua Town Centre;

• The Blue route eastbound follows SH1 southbound from Porirua Town Centre before turning onto SH2 northbound at the Ngauranga Interchange then to Lower Hutt Town Centre;

• The Green Route Westbound follows SH2 northbound from the Lower Hutt Town Centre before turning onto SH58 and heading westbound over to Pauatahanui Inlet. It then skirts the inlet until it reaches SH1 and which point it turns south until it reaches Porirua Town Centre; and

• The Green Route Eastbound follows SH1 northbound until it reaches Pauatahanui Inlet where it turns east and follows the inlet to SH58. From there it follows SH58 eastbound until it reaches SH2 where it turns south and carries on until it reaches Lower Hutt Town Centre.

Each of these routes can be seen on a map in Figure 4-8 and Figure 4-9.

Table 4-6: Travel times between Porirua and Lower Hutt Town Centres km km Route Route Period Period Direction Direction % Change %Change 2006-2026 2006-2026 2006 - 2026 2006 speed km/hr) km/hr) speed km/hr) speed Change (minutes) Change(minutes) Base 2006 (average 2006 Base Base 2026 (average 2026 Base Base 2006 (minutes) 2006 Base Base 2026 (Minutes) 2026 Base Average Speed change Speedchange Average AM Blue Westbound 22.6 30.36 31.81 1.45 5% 44.66 42.63 -5% Eastbound 22.5 21.47 27.43 5.96 28% 62.88 49.22 -22% Green Westbound 28.2 29.28 29.24 -0.04 0% 57.79 57.87 0% Eastbound 28.2 28.19 34.40 6.21 22% 60.02 49.19 -18% PM Blue Westbound 22.6 20.54 22.89 2.35 11% 66.02 59.24 -10% Eastbound 22.5 31.26 35.08 3.82 12% 43.19 38.48 -11% Green Westbound 28.2 28.59 32.32 3.73 13% 59.18 52.35 -12% Eastbound 28.2 30.33 30.71 0.38 1% 55.79 55.10 -1%

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Table 4-6 indicates that in the AM Peak the Green route eastbound is forecast to deteriorate with an increase in travel time of over 6 minutes between 2006 and 2026 (although this does not equate to the highest percentage increase). The same route and direction is forecast to experience a 18% decrease in average travel speed from 60km/hr in 2006 to 49km/hr in 2026. The Blue route is forecast to suffer similar levels of deterioration with an increase in just under 6 minutes and it is this route which shows the highest percentage increase in travel time when compared to the base with a change of +28%. The same route and direction is forecast to experience a 22% decrease in average travel speed from 63km/hr in 2006 to 49km/hr in 2026.

In the PM Peak, the Blue route continues to deteriorate in both directions with the eastbound direction, again, experiencing the worst increase (just under four minutes). The Green route however, only experiences a small increase in travel time in the eastbound direction with the westbound direction experiencing an increase of just under four minutes.

To gain an appreciation of which parts of the routes are contributing most to the increased travel times between 2006 and 2026 two figures have been produced. The figures display the routes selected for analysis and include a series of figures showing cumulative travel time plotted against distance:

• Figure 4-8 represents AM Peak. The Blue route eastbound travel time profile experiences a very large increase in travel time after 12kms in 2026, which is when the route reaches the Ngauranga Gorge interchange. The Green route eastbound experiences a large increase in travel time after 11kms in 2026 which is where the route reaches SH58; and

• Figure 4-9 represents the PM Peak. The Green route westbound experiences increase in travel times as soon as it reaches SH58 in 2026 whilst the blue routes experiences increases in travel times in both directions.

The plots clearly show the effect of excessive demand in Ngauranga Gorge and on SH58 on travel times.

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Figure 4-8 : AM Travel Time Routes

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Figure 4-9: PM Travel Time Routes

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4.5 Network Intervention Rationale

The purpose of this section is to summarise the justifications, or rationale, for a Porirua – Hutt Valley east-west link using findings from Section 0 to Section 4.5. The summary begins with the forecast assumptions which are characterised by:

• Uneven population growth where increases are concentrated in Wellington and Kapiti;

• Household growth rates of between 13% in Lower Hutt and 31% in Kapiti; and

• Employment with a much more even growth profile across the region (between 17% in the Wairarapa and 24% in Porirua).

Changes in landuse and demographics are forecast to have a major impact on overall private vehicle transport demand and distribution.

• 23% increase in trips across the region in the AM Peak. This is made up of:

− A 19% increase in trips originating from Porirua and 15% increase in trips originating from Lower Hutt. − A 23% increase in trips terminating in Porirua and 19% increase in trips terminating in Lower Hutt. • A 20% increase in trips across the region in the PM Peak. This is made up of:

− 20% increase in trips originating from Porirua and 16% increase in trips originating in Lower Hutt − 18% increase in trips terminating in Porirua and 14% increase in trips terminating in Lower Hutt. Forecast changes in demand and distribution are expected to put significant pressure on infrastructure. Base 2026 forecasts indicate increases of between 35% (in the AM Peak) and 44% (in the PM Peak) in vehicle kms travelled on congested links across the entire network. In terms of linking Hutt Valley and Porirua particular problems have been identified on the 2 main routes between these centres.

Capacity problems have been forecast to flow through to affect travel times between Porirua and Hutt Valley. This is shown in the modelling by the following travel times:

• In the AM Peak the green route eastbound is forecast to deteriorate with an increase in travel time of over 6 minutes between 2006 and 2026 (although this does not equate to the highest percentage increase). The same route and direction is forecast to experience a 18% decrease in average travel speed from 60 km/hr in 2006 to 49 km/hr in 2026. The blue route is forecast to suffer similar levels of deterioration with an increase in just under 6 minutes and it is this route which shows the highest percentage increase when compared to the base with a change of +28%. The same route and direction is forecast to experience a 22% decrease in average travel speed from 63km/hr in 2006 to 49km/hr in 2026.

• In the PM Peak, the blue route continues to deteriorate in both directions with the eastbound direction, again, experiencing the worst increase (just under four minutes). The Green Route however, only experiences a small increase in travel time in the eastbound direction with the westbound direction experiencing an increase of just under four minutes.

May 2011 Issue 2 32 Hutt Valley – Porirua Link Option Assessment Wellington Transport Strategy Model Analysis

The forecast deterioration in the performance of both main routes is one of the main reasons for developing the options described in Section 2. It was felt both options had the potential to significantly improve east-west access connections by:

• Providing a more direct link between the two town centres, and helping provide better access to new development areas in the case of the Petone Grenada link; and

• Easing congestion and thereby reducing journey times across an existing route in the case of the SH58 widening.

May 2011 Issue 2 33