Cellphone companies can already provide such information voluntarily. The bill would make it a legal requirement to do so when a law enforcement agency asks. It would also bar lawsuits against phone companies for doing so.
The measure passed the House last month and has been endorsed by a Senate commerce panel. It now goes to the full Senate.
Emergency dispatchers are already able to automatically pull up location information for most landline calls. But cellphone tracking could be used to find people who are missing or people who hang up before they can give their location.