The above (clickable) webcam gives you an insight into the traffic in both directions along Szentendre's Road 11 at the Lajosforrás and Református Gymnazium intersections. Scroll down at that page and you will also see a street view at Szentendre's Városkapu.
For webcams regarding Budapest's roads, please visit Budapest Közút, select 'Kamera' and then zoom in. (You can also download the Android/iOS app version here). To access web cameras for the roads outside Budapest, please follow this link and select 'Pest megye' in the menu bar on the left and then the camera that interests you. Alternately, follow the top and middle links/images to the right.
For a real-time look into Budapest's traffic congestion and roadworks, BKK offers this insight (in Hungarian) in association with WAZE's traffic outsmarting service and app. Alternately, follow the link/image bottom right.