Drive-through testing sites are open on various days of the week in Hertford, Watford, Hemel Hempstead, Stevenage and Welwyn Garden City for everyone living or working in Hertfordshire.The drive-through testing centre at Tesco Headquarters in Shire Park in Welwyn Garden City is open every day from 8am to 8pm. It has been carrying out an average of 210 tests every day. Here, people can test themselves with the swabs provided or have a swab test carried out by a trained professional. The test involves taking a swab of the nose and the back of the throat.Bring your mobile phone when you visit a testing centre. If you book a test in Watford, you may need to pay for parking as you wait.Visit www.gov.uk/coronavirus for more about symptoms, how to book a test and the NHS Test and Trace system.