otp_connect             Set up and confirm a connection to an OTP
                        instance.
otp_create_surface      Creates a travel time surface (OTPv1 only).
otp_evaluate_surface    Evaluates an existing travel time surface
                        (OTPv1 only).
otp_get_distance        Finds the distance in metres between supplied
                        origin and destination
otp_get_isochrone       Returns one or more travel time isochrones
                        (OTPv1 only)
otp_get_times           Queries OTP for the time or detailed itinerary
                        for a trip between an origin and destination
