Blog
The web speedometer is small. The questions around it are not. These posts cover the physics, the regulations, and the practical tests you can do with the phone in your pocket.
2026-08-30 · 7 min read
Almost nobody looks this up out of curiosity. A form wants the number, the dashboard shows three, and the one people pick by mistake understates the mileage by six figures. Which number it is, where to find it, and why it leans a percent or two in the seller’s favour.
2026-08-21 · 8 min read
The Department of Energy says yes, in most cases, but it stops being true on rolling hills, and the speed you set matters far more than the button. Plus the quirk nobody mentions: cruise control holds your indicated speed, not your real one.
2026-08-21 · 9 min read
Store a speed, read the sensor, compare, adjust the throttle, many times a second. What every button on the stalk does, how adaptive cruise differs from a speed limiter, and why the number it defends is the flattering one.
2026-08-21 · 8 min read
Cruise control almost never fails on its own. It gives up when one of its inputs goes quiet. Brake switch, fuse, clutch switch, speed signal, ABS, in that order, plus the sensor problems specific to adaptive systems.
2026-08-09 · 8 min read
CarPlay itself shows nothing — the projected app decides, and the big three give three different answers: Waze always, Google Maps only where a server-side rollout has reached you, Apple Maps never. The full map of what works, and why an enabled toggle can still show nothing.
2026-08-08 · 8 min read
Waze showing 67 while your dash shows 70 is not a bug in Waze — the dashboard is the biased instrument. Where the GPS number comes from, the three situations where Waze genuinely stumbles, and the speedometer settings worth a minute.
2026-08-07 · 9 min read
Apple Maps can flash a 65 sign at you while declining to mention you are doing 73. iOS 27 updates Flyover, offline maps and routing, and once again skips the one number drivers keep asking for. What the update actually changed, and the three working fixes.
2026-08-07 · 9 min read
Across 3 million fleet trips, an electric sedan runs 226 miles at 70 mph and 200 at 80, and a van gives up 39 percent of its range between 50 and 80. Why drag squares, why the measured loss is gentler than the physics predicts, and why in an EV speed is paid for in minutes rather than dollars.
2026-08-06 · 10 min read
Yes, and Progressive says so in its own terms. But on most programs speed is not what you are scored on: the rating lives in how fast your speed changes. What each program measures, where the 8 mph threshold really lands, and why phantom braking events happen.
2026-08-06 · 10 min read
Publication 463 asks for four elements on every business drive, and a GPS log captures three of them without you doing anything. The fourth is the one that gets deductions disallowed, and 2026 adds a second trap: the rate changed on July 1.
2026-08-04 · 9 min read
"Fines double in work zones" is exactly true in fewer states than people assume. Sixteen states compared across the three mechanisms they actually use, plus the condition that switches the enhancement on in the first place.
2026-08-04 · 8 min read
No federal rule requires a US car odometer to be accurate, and most read 1 to 3 percent high by design. What the standards actually say, why the error runs in one direction, and a GPS test that gives you your own number.
2026-08-04 · 9 min read
Towing behind a U-Haul caps you at 55 mph, the figure U-Haul publishes for its own trailers. Driving the truck alone, no major rental company publishes a maximum at all, so the limit is the sign, state law, and the loaded weight behind you.
2026-08-04 · 9 min read
Going 80 instead of 70 saves 32 minutes on a 300-mile trip and costs about $7.25 more in fuel, a fixed $13.54 per hour of time bought back. The full arithmetic, plus why the 55 mph sweet spot is wrong for hybrids and diesels.
2026-08-04 · 9 min read
50 mph is close to universal across owner's manuals, but the famous 70 miles figure is not in most of them. What 11 brands actually publish, why the limit exists, and what a smaller spare does to your speedometer, odometer and AWD system.
2026-07-02 · 10 min read
Police radar is accurate to about 1 mph, but tickets can still be wrong. The cosine effect, wrong-target reads, calibration gaps, and why your true GPS speed is the honest number on both sides.
2026-06-01 · 10 min read
Most Android phones can show your speed without a single Play Store download. Google Maps, Android Auto, the browser, and the apps worth installing, ranked by how much friction each one costs you.
2026-06-01 · 7 min read
KPH is kilometers per hour, the speed unit used by most of the world. What it means, how it differs from MPH, the exact conversion, and the mental math to switch between them in a second.
2026-06-01 · 9 min read
The "10% plus 2 mph" rule is guidance, not law, and it varies by country. What camera tolerance actually is, why your speedometer reading high already eats into it, and why GPS is the honest number.
2026-05-16 · 10 min read
Every smartphone has the hardware to be a precise speedometer. Choosing among hundreds of apps is the hard part. An honest comparison of the options that deserve your attention.
2026-08-19 · 9 min read
A dead speedometer is almost never a broken speedometer. Work the chain from fuse to sensor to cluster, let the odometer tell you which half to suspect, and use GPS until it is fixed.
2026-05-16 · 9 min read
Most cars do not need recalibration. The 4 mph optimistic dial at 70 mph is the law working as intended. When you actually need to recalibrate and what it costs in 2026.
2026-05-16 · 8 min read
The Apple Watch has a GPS chip but no single speedometer app. Three native ways to see speed (Workout, Maps, Compass), plus third-party options and accuracy notes.
2026-05-16 · 9 min read
The 3 to 5 mph gap between Google Maps and your dashboard is not a bug. Each one is measuring a different thing, and only one of them is the real ground speed.
2026-05-16 · 10 min read
The iPhone has a perfectly good GPS chip. Getting it to show you a speed reading is the hard part. Four ways to do it on a stock iPhone, three of them free.
2026-05-04 · 9 min read
Factory speedometers are calibrated to read 2 to 5 mph high. Here is the regulation, the math, and why a GPS reading is the honest one.
2026-05-04 · 8 min read
Modern phones report speed within ±0.5 to 2 mph. The accuracy comes from Doppler shift, not just position differences. A practical look at the numbers and the limits.
2026-05-04 · 7 min read
A 10-minute speedometer test you can do with your phone. Compare your dashboard against GPS at three speeds, calculate the offset, and decide whether to recalibrate.
