If you're a Sprint customer, here are the top five US cities where traffic jams might slow you down -- on your smartphone.

Thanks to some data crunching from Tutela Technologies, the below are Sprint's five most congested markets. These are the markets where Sprint's network is slowing down the most due to customer traffic. In other words, these are the cities where Sprint's network speeds are showing the biggest slowdown during peak usage times:

By contrast, here are the markets where Sprint's network is showing the best performance in terms of being able to keep pace with customers' demands:

In response to Tutela's findings, Sprint said it is currently increasing capacity and improving data speeds in all five of its "worst" markets by adding more 2.5 GHz spectrum. Also, in Escondido, the company said it is lighting up more 800MHz sites to improve data service.

But how did Tutela come up with these numbers?

Tutela inserts a tiny bit of testing software into some US smartphones, software that runs in the background and actively tests things like network speeds. To do this, Tutela works with Android and iOS app developers to get its software installed into their apps, and then that software runs in the background of those apps after mobile users download them. The company then collects and sells that data (which doesnt include any information that can identify a user or their device, including email addresses, IDFA, AAID, device ID, or IP addresses) and splits the resulting profits with participating app developers. The company counts over 3,000 participating app developers and over 250 million phones running its software.

For the above charts specifically, Tutela looked at the data from around 200 of the top markets in the United States. The company looked at the average speeds available during off-peak hours (basically in the middle of the night, when no one is using the network) and the average speeds available during on-peak hours (basically during afternoon rush hour, when everyone is using their phone) and compared the difference between those speeds. You can tell how congested a network is by how much slower it runs during peak times of usage.

Why is Sprint's network so congested in these five markets? Part of the reason may be due to the amount of spectrum Sprint is using in these markets. Tutela noted that, in the cities with higher network congestion, Sprint is using narrower spectrum bands and less total bandwidth on its 2.5GHz spectrum bands (the band that carries the most traffic for Sprint). The firm said that, on average, users had around 5MHz less bandwidth available on the 2.5GHz band in more congested markets when compared with lower congestion markets.

Finally, if you found this data interesting, just wait: We're going to publish similar results for the rest of the nation's big wireless network operators -- AT&T, Verizon and T-Mobile -- in the weeks to come.

 Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano