In December 2000, the LTSA and police introduced new Highway Traffic Patrols with greatly increased resourcing and rigid policies of speed limit enforcement.  The results are now clear.  Average speeds in both 100 km/h and 50 km/h zones have been forced down sharply, and ...

Rigid enforcement of speed limits has been a catastrophic failure!

• There has been a very large increase in injuries relative to the long term trends. 
• There has been a small increase in deaths relative to the long term trends.
• Detailed data charts show these effects have occured in all of the twelve NZ Police Districts.  Waikato District which had already suffered the adverse impact of the Waikato hidden speed camera trial immediately prior to the rigid enforcement introduction shows the least additional impact.  Southern District shows the worst impact.

In three years, rigid enforcement of speed limits by a vastly expanded highway patrol has reduced average speeds sharply but has cost New Zealanders over 11,000 extra road injuries and almost 50 extra deaths.

Note on the logarithmic scales used in the above graphs: 

The normal exponential growth equation is  y = e^ax where a is a constant, x is the time variable and y is the population measure.  (e is approx 2.718)  This equation applies in situations where the increase in population is proportional to the size of the population, for example where a population has a net increase of 2% per year.  (In that case a = 0.02 for x measured in years.)

The natural logarithm is defined to be:  ln(y) = ln(e^ax) = ax.   This means that if we plot ln(y) against x we get a straight line of slope = a.   This is the reason for using logarithmic scales in these charts.   On a normal flat scale we would be observing changes in curved lines - much harder to identify and measure.

We expect that the growth/decline of traffic casualties will be proportional to the total number of them - that indicates a steady trend and will be shown on a logarithmic plot as a straight line. 

This was in fact what we see 1994-2000 inclusive - a steady decline in all the death/injury statistics.  From 2000 onward that decline has reversed in three out of the four statistics as shown here numerically: 

Average Annual Changes	1994 through 2000	2001 through 2003
Deaths in 50 km/h zones	-13.0%	13.0%
Injuries in 50 km/h zones	-7.0%	10.4%
Deaths in 100 km/h zones	-1.6%	-2.3%
Injuries in 100 km/h zones	-3.4%	7.8%

The numbers of additional injuries caused by the new policies are estimated from the slopes of the above graphs prior to the LTSA policy and Police enforcement changes in December 2000 (see dotted lines on graphs) as follows (detailed calculations are all in the spreadsheet on the data page):

Year	Additional Injuries in 50 km/h zones	Additional Injuries in 100 km/h zones
2001	1383	870
2002	2878	1431
2003	3356	1840
TOTALS	7617	4140	Net Additional Injuries In Three Years	11,057

5,200 additional road crash injuries are now being inflicted on New Zealanders every year due to misdirected excessive enforcement policies which have had no measurable benefit in saving lives and may also have actually cost lives:

The numbers of additional deaths caused by the new policies are estimated from the slopes of the above graphs prior to the LTSA policy and Police enforcement changes in December 2000 (see dotted lines on graphs) as follows:

Year	50 km/h zones	100 km/h zones
2001	19	2
2002	18	-38
2003	43	4
TOTALS	80	-32	Net Additional Deaths In Three Years	48

The LTSA and police myth that lower average speeds reduce casualties and injuries has proven completely false.

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