Washington, DC (CNN Business) London's subway has become the latest transportation agency to use location data collected from people's smartphones in a bid to improve services.

Transport for London, which operates the Tube, began collecting data in its stations this week , in order to determine how people are moving through the system and how crowded trains and platforms are. It said passengers will benefit as they will get more alerts about delays and congestion later this year. Extra trains could also be added on routes where the data indicates trains are especially congested.

It's become increasingly common in recent years for transportation organizations worldwide to use smartphone data to better plan services. They say digital data offers insights that greatly surpass previous methods, such as user surveys.

But transportation experts believe London may have the first public transportation system to track and use individual trip data in real time. Given how large a system London operates, other cities may follow suit if the project succeeds. The practice also raises concerns about user privacy, unwanted tracking, potential hacks and the misuse of data.

In London, there is no process to obtain consent from passengers for the data collection aside from signs posted in stations, explaining that data is being collected to improve services. The signs also say people can opt out by turning off their wifi.

Read More