A circuit designer built for people who actually think about racing.

What is it?

RaceTrackDesigner is a free, browser-based application built for motorsport fans, sim-racing designers, and anyone who has ever looked at a stretch of road and wondered if it could be a race circuit. You place waypoints on a live map, and the application draws a smooth circuit through them, then analyses it to produce lap time estimates, speed zones, and a character rating.

The tool is built around the current Formula 1 calendar. It opens on Monaco by default, and all 24 circuits on this season's F1 schedule are available as presets in the location picker. You can of course navigate anywhere on Earth and start from scratch.

How does the circuit drawing work?

When you place waypoints, the track between them is drawn as a smooth Catmull-Rom curve rather than straight lines. The application respects the direction of approach into each waypoint, so the resulting circuit flows naturally without sharp kinks at each point. If you want a particular section to be perfectly straight — a pit straight or a Mulsanne-style runway — straight line mode is available from the Tools menu.

Every waypoint can be dragged in real time after placement. The track shape and all statistics update immediately as you drag. You can also double-click any waypoint to remove it, or undo up to 30 steps using Z or Ctrl+Z.

The track renders in two states. Before the loop is closed, it shows in a neutral tone to indicate the circuit is incomplete. Once you press C to complete the loop, the track switches to the speed zone colour system: red for full-speed sections, orange for fast corners, yellow for medium corners, and green for slow corners.

Shaping the tarmac

The default track is 8 metres wide with 14 metres of runoff on each side, but every part of the geometry is editable. Each segment between two waypoints can have its own track width — and the left and right sides of the tarmac can be set independently, so you can model the asymmetric widening that real circuits use to encourage overtaking on the inside of a corner. Blue handles on the map let you drag widths directly; the Tools menu opens a full panel for numeric input on every segment.

Kerbs can be placed along corners and chicanes from the Tools menu — useful for visualising apex placement and exit lines. The pit lane is drawn separately alongside the main track and can be toggled on and off independently. Runoff areas extend to either side of the tarmac and can be shaped the same way as the track itself.

Turn labels (T1, T2, T3…) appear automatically at every detected apex once the loop is closed. If the automatic placement doesn't match what you want — say, you want "Eau Rouge" to label a sequence rather than a single corner — custom turn labels let you manually define where a turn starts and ends and give it any name.

How does the physics model work?

The model measures the curvature of the track at every point and derives a maximum cornering speed based on the grip and downforce characteristics of the selected vehicle class. Tighter corners produce lower speed limits; sweeping curves allow much higher speeds.

Once corner speeds are established, the model applies the acceleration and braking capabilities of the car to build a continuous speed profile across the full lap. This gives you realistic top speeds, minimum speeds, and a lap time that accounts for how long it actually takes to slow down and accelerate back out of each corner.

Lap time and race laps are calculated from this profile. The results are approximations rather than a full simulation, but they are grounded in real vehicle physics and produce numbers that feel right to anyone familiar with motorsport.

The six vehicle classes

Each class has a distinct set of performance characteristics. Switching between them on the same circuit is one of the most revealing things you can do — tight corners that barely register for an F1 car become significant obstacles in GT3, and corners that GT3 handles comfortably can be genuinely slow on a kart.

Formula 1 generates extreme levels of aerodynamic downforce that increase with speed. This means F1 actually corners more efficiently at higher speeds, producing a non-linear relationship between corner radius and minimum speed. The class is configured around a 305 km race distance, matching the minimum FIA Formula 1 distance.

GT3 represents a more accessible category derived from production road cars. It produces less downforce and lower lateral grip than F1, which makes medium-speed corners noticeably slower and gives the class a different rhythm through the same layout. Race distance is set to 100 km.

MotoGP has the lowest cornering grip of the four-wheel-and-two-wheel classes, reflecting the physics of a motorcycle versus a four-wheeled car through the same corner. Despite this, the extraordinary power-to-mass ratio of a MotoGP machine means it matches F1 for top speed on long straights. Race distance is 110 km.

IndyCar is open-wheel racing built for both ovals and road courses. The model is less downforce-dependent than F1 and has a flatter cornering profile, which makes it rewarding on entirely different layouts — high-speed ovals where minimum speed barely drops, or tight street circuits where braking points decide everything.

NASCAR represents heavy stock cars — 1,540 kg of metal with 500 kW under the hood and a 290 km/h top end. Lower cornering grip than the open-wheel classes and a much higher mass produce braking zones that demand respect, with a 400 km race distance reflecting the real-world endurance of stock car racing.

Go Kart uses a 180 kg shifter kart with 22 kW and no aero to speak of. The speed range is smaller — 130 km/h top speed — but the differences between corners are sharper, which is why the speed zone thresholds are scaled down specifically for kart-scale racing. Use it to lay out kart circuits at their natural size, with a 15 km race distance.

Speed zones and circuit character

Once the loop is closed, each segment of the track is coloured according to its calculated speed. The four zones are full speed (red), fast corners (orange), medium corners (yellow), and slow corners (green). The thresholds are calibrated per class, so the same corner will show a different colour in F1 versus GT3.

The circuit also receives a character rating based on how many corners it has relative to its length. The four ratings are Ultra Technical, Technical, Balanced, and High Speed. The rating, corner count, and longest straight are all shown in the track analysis panel alongside the speed statistics.

Export and sharing

You can export your circuit in three file formats from the Settings menu: GPX for sim racing software and GPS devices, KML for Google Earth and other geographic viewers, and XML for the raw waypoint and segment data. Keyboard shortcuts G, K, and X jump straight to each format.

The share link encodes your entire circuit into a URL. Anyone who opens it sees the circuit exactly as you left it and can continue editing. Nothing is stored on any server — the circuit lives entirely in the link.

Platform and compatibility

The app runs entirely in your browser with no installation required. It works best on desktop, where the full interface is available. Mobile is supported with touch gestures for placing, dragging, and zooming, though some features are simplified on smaller screens. No account or login is needed, and nothing you design is stored anywhere.