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 51% lower while the lower limit applied (compared with before), and 35% higher 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
32
7
5
Injury crashes
11
3
3
Death or serious injury crashes
5
1
0
Fatal crashes
2
0
0
Crashes per month
0.53
0.28
0.38
Crashes per million vehicle-days*
1.10
0.54
0.73
*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
6% fewer95% CI -80% to +329% · p = 0.933 · not statistically clear
All crashes · after limit raised
40% fewer95% CI -98% to +1660% · p = 0.767 · not statistically clear
Injury crashes · while lower limit applied
43% fewer95% CI -97% to +952% · p = 0.702 · not statistically clear
Injury crashes · after limit raised
68% fewer95% CI -99% to +1745% · p = 0.584 · not statistically clear
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.