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How police car top speed stopped meaning anything
In 2016 a Dodge Charger needed thirteen miles to reach 150 mph. The following year the same car got to 149 in a mile and a half. Nothing about it had changed.
For most of the last century, the top speed of a police car was a fact about the car. You put your foot down, you held it there, and eventually the vehicle stopped going any faster because it had run out of engine, or gearing, or air to push through. The number that came back described something real.
That is no longer true, and we can say so precisely — because the Michigan State Police started publishing the one piece of information that gives the game away.
The column that changed everything
In its 2016 evaluation, Michigan added a measurement it had never printed before: not just the top speed each vehicle reached, but the distance it needed to reach it. Every car gets fourteen miles of proving ground from a standing start. The new column recorded how much of that it actually used.
On its own it reads like housekeeping. Read two consecutive years of the same car and it is something else entirely.
| Dodge Charger 5.7 HEMI, rear-drive | Top speed | Distance needed |
|---|---|---|
| 2016 | 150 mph | 13.28 miles |
| 2017 | 149 mph | 1.45 miles |
One mile an hour slower, and it arrived there in a ninth of the distance. The 2016 car was still gaining speed after thirteen miles — it used almost the entire allowance and was arguably still climbing when the road ran out. The 2017 car was finished inside a mile and a half and then simply held there.
That is not an engine change. Nothing about a 5.7-litre HEMI alters to produce that result. It is a number in the engine management software.
A car that spent thirteen miles climbing to 150 mph was replaced by one that reached its ceiling in ninety seconds of hard acceleration — and the published top speed barely moved.
The Caprice tells the same story more quietly. In 2016 the 6.0-litre car reached 155 mph after 6.62 miles. In 2017 it reached the identical 155 mph after 3.21. Same figure in the results table, half the road to get there.
Where the limiters came from
They did not appear overnight, and they appear earlier in the Michigan record than this article first claimed. The footnote “Vehicle equipped with speed limiter” is already in the 1995 book.
1996 shows what that meant in practice, because the same table contains both kinds of car. The Caprice’s 139 mph carries no footnote — that is a measurement. The Crown Victoria’s 135 carries one, as do the 4.3-litre Caprice at 120, the Jeep Cherokee at 112, the CNG Crown Victoria at 107 and the Ford Explorer at 106. Five of the ten vehicles in that test were reporting a setting rather than a capability, and Michigan said so in a single asterisk.
By 1998 it had spread: ten of the fifteen vehicles tested carry the limiter footnote. The Crown Victoria’s 130 mph, the Explorers’ 106, the Expedition’s 106 — none of those describe what the vehicle could do. They describe what its manufacturer had decided to permit.
The same book contains a second footnote that is almost funnier. Both Camaros are credited with exactly 150 mph, with a note explaining that drivers were instructed not to exceed 150 because of the limitations of the test track. The bulletin’s own stated objective had by then been rewritten to read “up to 150 mph.” A year earlier a Camaro had run 157. The fastest cars in the programme had outgrown the place they were measured.
Both problems were eventually solved. The tests moved to a proving ground with room to run, and by 2000 a Camaro recorded a genuine 160 mph. But by then the limiters were spreading, and the bulletin still carried the stale “up to 150 mph” objective on a page where four vehicles exceeded it.
What a governed police car looks like in the results
Once you know to look for it, the pattern is unmistakable. From 2016, the same test:
| Vehicle | Top speed | Reached after |
|---|---|---|
| Dodge Charger 5.7 (rear-drive) | 150 mph | 13.28 miles |
| Dodge Charger 3.6 (3.08 axle) | 142 mph | 11.78 miles |
| Chevrolet Caprice 3.6 | 146 mph | 7.91 miles |
| Chevrolet Tahoe 5.3 4WD | 121 mph | 1.26 miles |
| Ford PI Sedan 2.0 EcoBoost | 120 mph | 1.66 miles |
The vehicles at the top of that table are still accelerating when they run out of road — that is what eleven and thirteen miles means. The ones at the bottom arrive at a hard ceiling almost immediately and sit against it. A governed vehicle does not gradually approach its maximum; it hits a wall.
By 2017 the wall was nearly universal. Only one vehicle in the entire field still needed more than 3.21 miles to find its top speed — the 3.6-litre Caprice, at 9.91 miles. It is also the only car whose top speed had barely moved in three years. Nobody had got round to governing it.
The consequence for the record
This matters for anyone who reads these tables historically, which is the entire point of keeping an archive of them.
When the 1980 book records a Plymouth Gran Fury at 124.6 mph, that is a measurement. When the 1996 book records the last Caprice at 139 mph, that is a measurement, and it stood as the fastest police sedan in the programme for sixteen years. When the 2011 book records a Ford Police Interceptor at 119 mph — slower than both Impalas, both Tahoes, both Caprices and a V6 Charger in the same test — that is not a measurement of the car. It is a measurement of a decision made in Dearborn.
Comparing those three numbers as though they describe the same kind of fact produces nonsense. The Panther-platform Crown Victoria did not become slower than a Tahoe. It became more thoroughly restricted than one.
The top-speed column used to answer “how fast will it go?” Now it mostly answers “how fast has someone decided to let it go?” — and only the distance column tells you which question you are reading.
Why manufacturers do it, and why Michigan keeps measuring anyway
The reasons are not sinister. A speed limiter is usually a tyre decision: a vehicle is governed to the sustained speed rating of the rubber it leaves the factory on. It can also be a cooling decision, a driveline decision, or a liability decision. Nothing in the Michigan books suggests otherwise, and the books do not editorialise about it.
What Michigan does instead is more useful. Its published purchasing specification — printed in full in the 2019 book — barely mentions top speed as a headline figure at all. What it requires is that a vehicle reach 110 mph within 4,838 feet and 120 mph within 8,985 feet. Those are distance requirements, not speed ones. They ask how quickly a car can get to a useful speed, which is a question about an actual pursuit, rather than what number it can eventually reach on fourteen miles of empty road, which is not.
In other words, the programme had already stopped believing in the top-speed column before it gave the rest of us the tool to see why.
How to read a top speed now
Three rules, which apply to any Michigan figure from 1998 onward:
A round number is a limiter. 130, 120, 106, 100. Measured top speeds are untidy — 124.6, 137.2, 146.6. Manufacturers set limiters at round figures.
A short distance is a limiter. Anything arriving at its maximum inside two miles has been told to stop. Genuine top speeds take most of the fourteen.
Identical figures across years are a limiter. Real measurements wobble year to year with weather, tyres and the particular car submitted. A number that repeats exactly is a setting, not a result.
Apply those three and the tables come back to life. You can see precisely which vehicles in any given year were being measured, and which were merely being reported.