The racing line,
solved.
Apex Lines computes the ideal line for 18 real US circuits from the track geometry itself — then lets you study it on a map, fly it in 3D, and log every session against it. Offline-first, no account, one app on iPhone and Mac.
18 real US circuits line solved from geometry offline-first · no account
Solved, not sketched.
Most track maps come with an artist's swoosh. Apex Lines runs a minimum-curvature optimization over each circuit's real pavement corridor, so the line you study is the one the geometry actually supports.
Minimum curvature
The line is the solution to a math problem — the smoothest path the pavement allows — not a hand-drawn suggestion. Same method, all 18 circuits, no house style.
Apexes that are real
Every apex falls where the solver puts it, tight against the inside edge. Late apexes emerge from the track shape, because that's where the math clips the corner.
Contained on asphalt
The solver works inside the track boundaries, so the line never cuts grass or hangs over a kerb that isn't there. If it's on the map, it fits on the pavement.
Watch a lap fly itself.
Every circuit renders as a full 3D scene, and fly-the-line mode runs a physics-flavored lap over the computed line — braking into corners, driving out of them — with a live HUD the whole way around.
- Grip, braking and drive limits shape the speed profile — and you can tune them.
- Live HUD: speed, ride state, and the next corner coming at you.
- Flip between the 2D map and the 3D scene on any track.
Pro · 3D scene and fly-the-line
Every corner, briefed.
Each turn gets a guide derived from the line's curvature: radius, arc, run-up, and the classic racecraft reference points — brake, turn-in, apex, exit — so you walk the track before you ride it.
- Per-corner radius, arc and run-up, measured from the solved line.
- Brake / turn-in / apex / exit references on every corner.
- Corner notes in the notebook attach to the same map, so your experience layers onto the geometry.
Pro · corner guides
A notebook that lives at the track.
Track days hold sessions, sessions hold laps. Log times with a stopwatch-style field built for gloves-off pit lane moments, tag tire pressures and weather, pin notes to corners on a mini map — then watch the trend line fall.
- Lap trends charted per track, with personal bests tracked automatically.
- Tire pressures, weather, and per-corner notes on every session.
- One-handed flow on iPhone; a three-pane logbook on Mac.
Free for your first track day · Pro · unlimited
OCT 12 · 3 SESSIONS · 14 LAPS
- S2 · LAP 42:05.31
- S3 · LAP 22:03.88
- S3 · LAP 5 PB2:02.47
18 circuits. Real geometry.
Every outline below is the actual track data in the app — and every red line is its solved ideal line. Search and filter the library by region, length, and character.
WeatherTech Raceway Laguna Seca
Circuit of The Americas
Road America
Michelin Raceway Road Atlanta
Barber Motorsports Park
Virginia International Raceway
Sonoma Raceway
Willow Springs (Big Willow)
Streets of Willow Springs
Buttonwillow Raceway Park
Thunderhill East
The Ridge Motorsports Park
Pittsburgh Int'l Race Complex
NJMP — Thunderbolt
Mid-Ohio Sports Car Course
Watkins Glen International
Sebring International Raceway
Utah Motorsports Campus
TRACK OUTLINES © OPENSTREETMAP CONTRIBUTORS · ODbL
Log at the track. Study at home.
Built for pit lane
A fast, one-handed flow for the ten minutes between sessions: punch in lap times, tire pressures and weather, drop a note on the corner that's bugging you. Fully offline — paddock signal doesn't matter.
Built for homework
A three-pane logbook with lap-trend charts, and the whole track library on a big screen — walk the line corner by corner and plan the next day out. One purchase covers both platforms.
No account to create. Your notebook is stored on-device and syncs between your iPhone and Mac through your own iCloud.
A free tier that's actually useful.
Every circuit and every solved line is free. Pro opens the rest of the toolbox.
- All 18 circuits, with search and filters
- 2D maps with the full computed racing line
- Your first track day in the notebook
- Track-day prep checklists and references
- Metric or imperial, app-wide
- Everything in Free
- 3D scenes + fly-the-line simulation
- Corner guides on every turn
- Unlimited notebook
- Everything in Pro Monthly
- One season, one payment
Prices in USD; local pricing may vary. Subscriptions bill through your Apple ID and renew until cancelled — manage or cancel anytime in Settings. One subscription covers iPhone and Mac.
Fair questions.
Is Apex Lines a GPS lap timer?
No — and that's deliberate. Apex Lines is the study-and-logging half of your track day: you learn the line before the day and log what happened after each session. Lap times come from whatever times you — a transponder, a timing app, or the org's printout — and the notebook's stopwatch-style field makes punching them in quick.
Where does the track data come from?
Circuit geometry is derived from OpenStreetMap (© OpenStreetMap contributors, licensed ODbL). The racing line, corner guides and everything built on top are computed by Apex Lines from that geometry. Apex Lines is fully independent — no affiliation with any track, school, or series.
Does it need a connection at the track?
No. Everything — tracks, lines, guides, notebook — works fully offline. There's no account to sign into. iCloud sync between your devices happens automatically whenever you're back online.
What exactly is free?
The complete 18-circuit library with the full computed racing line on the 2D map, prep checklists, and your first track day in the notebook. Pro adds the 3D scene with fly-the-line, corner guides, and an unlimited notebook — $4.99/month or $39.99/year.
Which devices does it run on?
iPhone (iOS 17 or later) and Mac (macOS 14 or later). It's one native SwiftUI app on both, and one subscription covers both.