Make Tunnels navigable
Great news! The Waze Beacons Program is in the works and constantly expanding.
The Waze Beacons Program is the first scalable, affordable solution in the world to power navigation in tunnels. Currently available in select tunnels throughout Pittsburgh, Haifa, Israel, Paris and Rio de Janeiro – seamless navigation is available to Wazers underground simply by turning on Bluetooth functionality.
perhaps use phone's accelerometer to estimate change in movement?
Erik Näsström commented
I think tomtom and others have been doing this for a while, and it's pretty simple!
you have the speed at the entrance just keep the icon moving at the same speed when you loose the signal entering the tunnel and correct any eventual errors once you exit and get contact again!
Or you can calculate the general speed by taking the distance / time in tunnel and set the "car" to move in that pace and then correct it once you enter!
Sure, it won't be a 100% match always, but it's one way to do it!
How exactly are you planning to do this without GPS? If there is no GPS available (such as in tunnels), you need to depend on cellphone towers, but these are inaccurate in displaying the exact location (and several tunnels do not have towers, but have the signals coming from outside (or beginning/end of) the tunnel).