live, ‘as it happends’ is probably not possible.
I don’t know how fast the cars are moving and how many cars passes your sensor every minute.
so depending on that answer its better to collect some data (count cars) and transmit that number with a certain interval, that way you always stay within the fair access policy
see Limitations: data rate, packet size, 30 seconds uplink and 10 messages downlink per day Fair Access Policy