Final answer:
The default speed limit in residential areas is often 25 mph, but it can vary by jurisdiction. Always check local signage for variations. Typically 30 mph, which is about 50 km/h, might be the default in some areas.
Step-by-step explanation:
Unless otherwise posted, the speed limit in a subdivision or residential neighborhood is typically around 25 mph or roughly 40 km/h. However, this can vary depending on the jurisdiction and local laws. In some areas, the default residential speed limit may indeed be set to 30 mph, which is approximately 50 km/h.
It's important to always check for posted signage that may indicate a speed limit different to the default. Driving behavior, like that in Jacinto City, Texas, suggests the norm of driving around the speed limit, with slight leeway for minor over-speeding due to the inaccuracy of speedometers, but pushing further can result in a traffic violation.