Flat Bush · lowered 26 January 2023, raised again 20 March 2025
Before
60 km/h
until 26 January 2023
Lower limit
50 km/h
26 January 2023 to 20 March 2025
Raised again
60 km/h
from 20 March 2025
Where the crashes happened
The blue line is the official Auckland Transport speed-change geometry for this section. Each dot is a crash that CAS places on the treated road; colours show which speed-limit period it fell in. Larger red-ringed dots are crashes in which someone died or was seriously injured.
BeforeDuring lower limitAfter raisedDeath or serious injury
What the monthly record shows
Adjusted for Auckland-wide traffic trends, the observed crash rate was 3% lower while the lower limit applied (compared with before), and 100% lower after the limit went back up (compared with the lower-limit period). Single-road counts are noisy, so read this alongside the pooled estimate on the corridor results page.
Measure
Before (60 mo)
Lower limit (25 mo)
Raised (13 mo)
All crashes
23
10
0
Injury crashes
7
4
0
Death or serious injury crashes
1
1
0
Fatal crashes
0
0
0
Crashes per month
0.38
0.40
0.00
Crashes per million vehicle-days*
1.45
1.41
0.00
*Traffic exposure uses this road’s baseline daily traffic trended by the Auckland-wide TMS fixed-site index.
This road’s own model estimates
A segmented Poisson time-series model fitted to this road alone, with terms for the underlying trend and for level changes at the lowering and the raising. Confidence intervals on a single road are wide; the pooled 24-corridor models are the headline evidence.
All crashes · while lower limit applied
193% more95% CI -54% to +1781% · p = 0.258 · not statistically clear
All crashes · after limit raised
No crashes recordedafter the limit was raised (to the data cut-off)
Injury crashes · while lower limit applied
Too few crashesfor a road-level model; this road still contributes to the pooled estimate
Injury crashes · after limit raised
No crashes recordedafter the limit was raised (to the data cut-off)
Crash records are complete to 30 April 2026 (later months are still filling in), so the after-raising period is still short. Estimates for this single road will firm up as more months accumulate; the full method, sensitivity checks and audit files are on the main report page.