These days, most people have access to the internet to look up anything they may need. While you may be used to doing a quick search on your phone, you can't do that while you're driving. That's where 511 comes in.
Many states allow drivers to dial 511 on their phone in order to get current traffic information. The information you can gain from dialing 511 depends on the region you're calling from. Some services will give you information on road conditions only, while others will tell you about construction sites, public transportation, collisions, and detours.
Using 511 to gather information about traffic conditions is a safer way to find information when you're behind the wheel, rather than reading information on your phone.