Memorandum 
To 
Tony Innes / Megan Wheeler 
From 
s 9(2)(a)
Copy 
Scott Elwarth; Daryl Lim 
Document Code 
10722-PTA-230-TR-MEM-0004 
Date 
October 2025 
Pages  
3 
(including this page)
Subject 
Reported Travel Time Savings in the Investment Case 
Purpose 
ACT 1982
This technical note summarises how travel time savings reported in the Northland Corridor 
Investment Case were calculated. 
Background 
Two complementary approaches were applied to estimate potential savings across the 
corridor: 
• Observed data assessment – based on 2025 weekday travel times, providing an
INFORMATION 
indicative estimate of potential savings under existing conditions; and
• Model-based assessment – using the updated Northland Corridor full corridor
traffic model for the 2054 forecast year, supported by SIDRA network modelling for
Section 3B, to provide an assessment of long-term performance.
While both approaches were consistent in demonstrating travel time savings across the 
corridor, the model-based assessment formed the basis of the economic evaluation as it 
provided average conditions and should be seen as a conservative estimate of the long-
term corridor performance. The observed data was used primarily to illustrate the potential 
scale of benefits under a range of travel time conditions. 
Observed Data 
Observed weekday travel times in May 2025 along the existing SH1 route from 52 minutes 
to 82 minutes across the 73-kilometre length of SH1 (Sections 2A to 3B). 
The corresponding potential travel time savings on the proposed Highway ranges from 7.8 
minutes under uncongested conditions to 37.8 minutes (assuming the upper range 
congestion levels are resolved).  This was based on an assumed operational speed of 
105km/hr on the new highway (Section 2A to 3A). Section 3B is split between 75km/hr 
RELEASED UNDER THE OFFICIAL 
(peri-urban) and 45km/hr for the urban section. 
Document Code: 10722-PTA-230-TR-MEM-0004 
Revision: A 
Page 1 of 3 

---

Memorandum 
Table 1: Typical Weekday Travel Time Savings (May 2025) 
Observed Range of Weekday Travel 
Range of Typical Weekday Travel 
Times along existing SH1 
Time Savings (mins) using new 
(mins, May 2025) 
Highway 
ACT 1982
General traffic 
Lower 
Upper 
Lower 
Upper 
Section 2A 
14 
20 
2.9 
8.9 
Section 2B 
10 
16 
1.5 
7.5 
Section 2C 
8 
10 
2.0 
4.0 
Section 3A 
14 
22 
0.9 
8.9 
INFORMATION 
Section 3B 
6 
14 
0.5 
8.5 
Total 
52 
82 
7.8 
37.8 
Typical weekday travel times along the full corridor currently vary considerably between 
uncongested and heavily congested conditions, as demonstrated above and illustrated by 
Labour Day travel patterns. 
On Labour Day morning, travel between Loop Road and Te Hana was relatively smooth, 
averaging 84 km/h and taking approximately 47 minutes to cover the 66-kilometre stretch 
(noting this is slightly shorter than the full project corridor between Te Hana and 
Whangārei). 
By contrast, southbound traffic volumes increased sharply in the afternoon, with the most 
severe delays occurring between 3:00–4:00 pm, when average speeds fell to 46.9 km/h and 
journey times extended to 84 minutes. 
These Labour Day travel times closely align with the upper end of the observed weekday 
travel time range in Table 1. 
RELEASED UNDER THE OFFICIAL 
Document Code: 10722-PTA-230-TR-MEM-0004 
Revision: A 
Page 2 of 3 

---

Memorandum 
Model-Based Output 
Model outputs were available for Sections 2A–3A (Te Hana to Loop Road) from the full 
corridor model, while Section 3B was assessed separately using SIDRA intersection 
modelling. 
Weekday travel time savings on the highway, relative to the existing SH1 route, were 
modelled for the 2054 model year, refer to Table 2 below. 
ACT 1982
Table 2: Typical Weekday Travel Time Savings 2054 forecast period 
AM Peak 
PM Peak 
Year 
Source 
Section 
Savings 
Savings 
(minutes) 
(minutes) 
2054 
Corridor Model 
2A–3A 
12.0 
19.2 
INFORMATION 
2054 
SIDRA 
3B 
16.0 
15.8 
Corridor Model / 
Total 
2A-3B 
28.0 
35.0 
SIDRA 
The travel time savings derived from the model are comparable with the observed results 
presented in Table 1. Travel times are forecast to reduce from approximately 74 minutes to 
46 minutes during the AM peak, with similar reductions observed during the PM peak (refer 
to Table 3 below).  
Table 3: Typical Weekday Travel Times 2054 forecast period 
Corridor 
Travel Times (AM) 
Travel Time (PM) 
(Old) SH1 Route Travel time 
74.5 
81.6 
 (Section 2A-3B) 
New Highway Travel Time  
46.5 
45.6 
(Section 2A-3B) 
Conclusion 
RELEASED UNDER THE OFFICIAL 
Both observed and model-based assessments demonstrated consistent patterns of travel 
time savings.  
Document Code: 10722-PTA-230-TR-MEM-0004 
Revision: A 
Page 3 of 3 

---