Type "Taxi1" will get the taxi to drive you fast.

More extras
"taxi2" will have the taxi drive very normally, and stop at the traffic lights
"taxi3" Will bring Bobby with Huntley to drive you faster.

Enter the taxi as a passenger by pressing the ENTER, then to put a target marker on the map, and then press
"conversation - no"/N to have him drive you to your destination. For second player, he can also get in as a passenger too.
To cancel press ENTER to exit the taxi.

NOTE: You won't skip the ride just like GTAIV or GTAV!