It’s all about integrity. In theory, radio cabs should hit the meter the second they take a call. That means a cab arriving in three minutes (write down the “sigla,” or ID no., as in “Palermo 53”) should get to you three minutes from when he took the call and started the meter. Same with five, eight, 10, and so on. The longer the wait, the higher the price on the meter because it assumes a longer trip to come and fetch you. Traffic is a wild card. A cab coming in three can sometimes take 10. That’s life. It’s also annoying and upsetting, particularly when he or she arrives with €15 on the meter. You can refuse so long as you instruct your hotel or restaurant to explain your refusal. Walking away is both impolite and reckless. Have the hotel concierge, the cashier at the restaurant, or even the driver call the “centrale,” the dispatch, to explain your concern. In general, cab drivers are honest. The meter is hard to “fix” or manipulate. A rule of thumb is to assume three minutes will be five, and so on. Another one is to expect a radio cab will arrive with at least €4/5 on the meter, so you can consider your fare from that baseline.