My title is meant to be humorous, but there's truth to it. It's obvious there's no traffic when people are asleep at night, but did you know that Vietnamese sleep at noon? Many businesses close shops between 11:30-1:30 everyday for lunch and nap. (I emphasized "everyday" because they work 7 days a week.)
I don't know how the culture of napping after lunch started, but I can only guess one reason--no one wants to drive around during the hottest time of the day. As a result, you won't see that many people on the street during noon time.
Vietnam doesn't have daylight time saving, but they really schedule their activities around the sun to achieve a productive day. In addition to napping during lunch time, they wake up very early to enjoy a beautiful and cooler morning. On the same token, they also go to sleep early so they can wake up early the next morning. Those activities also conserve energy use too.
So if you don't want to put up with traffic, travel around 11:30-1:30. But don't do business during that time because no one will meet you. =)
Please feel free to explore other photos in my #rediscovervietnam series.