Frequently asked questions

What is Traffic Watch?

A free, open source app that shows how long it currently takes to drive into central Warsaw from 12 city entry points, from Łomianki and Jabłonna to Piaseczno, Raszyn and Pruszków. You can see the whole day, compare it with a typical day of the week, and compare day with night.

The “My commute” tab calculates the trip between your home and work by car, public transport or bike and tells you when it is best to leave.

Where does the data come from?

Car travel times and forecasts come from Amazon Location Service (the HERE engine with traffic data). Public transport uses the same service in transit mode, based on ZTM timetables. Bike routes are calculated by Valhalla on OpenStreetMap data. The map is OpenFreeMap.

We checked the city's open data. The roads authority (ZDM) publishes traffic volumes, not travel times, and the city API has no journey planner, so we measure travel times ourselves.

How often are measurements taken?

Every 15 minutes between 5:00 and 23:00 and hourly at night. Each measurement covers 12 routes from the entry points to Rondo Dmowskiego.

What do “average travel time” and “vs. empty road” mean?

The average travel time is the mean of the 12 routes, with longer routes weighted more. “Empty road” is the travel time without traffic, so “+30%” means the trip takes 30% longer than on empty streets at night.

Colours: green is free flow, yellow moderate, orange heavy traffic, red gridlock.

Where does the “usual” line come from?

It is the average of all previous measurements at the same time on the same day of the week. The longer the app runs, the more accurate it gets.

How does “My commute” work?

Type your home and work addresses or pick them on the map. For car and public transport we calculate 26 departure times: mornings from 5:30 to 10:30, afternoons from 14:00 to 20:00 and at night at 3:00. Clicking a bar shows the details and the route on the map.

Car uses a traffic forecast based on history. Public transport is door to door, including walking and waiting at the stop. Bike assumes relaxed city riding at about 18 km/h.

How accurate is the forecast?

It is based on typical traffic for that day of the week and time. It cannot predict an accident, roadworks or a sudden closure, so treat it as a guide to when the trip is usually fastest.

Why must both points be within 60 km of the centre?

The app is about commuting in the Warsaw metropolitan area, and the limit protects the paid routing services from abuse.

Does the site use cookies?

No. We use no cookies and no identifiers stored in your browser, so there is no consent banner.

Browser storage (localStorage) only keeps your settings: language, mode of transport and your home and work points. They only leave your device as part of a route request.

How do you count visits?

We only keep aggregate statistics: page views, the referring domain, language, device type and country. Daily unique visitors are counted with a hash of the IP address and browser that changes every day and is deleted after two days. The IP address itself is never stored.

If Do Not Track or Global Privacy Control is enabled, nothing is sent.

What happens to my home and work addresses?

For the calculation we round the points to about 100 m. The result is cached for 7 days so we do not calculate the same trip twice, keyed by a hash rather than the coordinates. Address suggestions are never stored.

Can I add a city, an entry point or a fix?

Yes, the code is open source under the MIT licence: github.com/Tuhaj/traffic-watch-2026. Report an idea or a bug in Issues, or open a pull request. A new entry point is a single line in shared/cities.ts.

Who made this?

Piotr Zientara. The first version was built in 2014 as an open source project with the support of mentors at Rebased: Bernard Potocki, Krzysztof Modras and Tomasz Stachewicz. In 2026 the app was rewritten from scratch.