The bus has a figure of Guanyin (a Buddhist deity) and incense burning in the front. It must be safe.
If you search the internet looking for how to get from Da Nang to Hoi An, nearby coastal cities in central Vietnam, you will probably find articles stating that the yellow bus from Da Nang to Hoi An is a scam—that it charges foreigners 50,000 VND (US$2.22) or so and Vietnamese 20,000 VND (US$0.89).
Well, I just took the yellow bus today to get to Hoi An, and they only charged me 20,000 VND. In fact, I had already pulled out 20,000 and gave it to the money collector, having read up on the possible scam. The money collector said something to me after, as I was sitting in the seat—possibly to the effect of the price being cheap and possibly wanting me to give more, but I don’t know, because I can’t speak Vietnamese, and her English was poor—but whatever she said it didn’t matter because I ignored her and remained seated.
(Some sources say the ticket price is 18,000 VND, but it is normal for Vietnamese to not give change for something less than 5,000 VND (US$0.22).)
They didn’t give me a ticket, by the way, nor did I see them give anyone else a ticket, so do not feel uneasy about them not giving you a ticket.
Here are some other travelers who have talked about getting scammed by the buses:
Jay and Jon, June 2013
TripAdvisor forum, August 2011
Cafes with flower-covered roofs in Hoi An.
As noted, the scam—if it still occurs—appears to be easily avoidable. Just have the 20,000 VND bill(s) ready and give them the exact amount and ignore any hassling after you sit down. One of the other commenters also notes—and this is probably a good idea—to not give them more than 20,000, as they might not give you change.
This, too, is good advice for when you get off at the Hoi An bus station in Da Nang and must get to the ancient city. There is a big map at the bus station, so you can easily find the way to get there yourself by walking, however it could be 30 minutes or more, depending on where your hotel is located, so you may want to take one of the many motorbikes.
I took a motorbike after agreeing to 15,000 VND for the ride. The driver originally asked 20,000 VND, and I asked 10,000, and then I raised to 15,000 and started walking after he denied that. Later, he drove up beside me and agreed to 15,000, and I got on. When we arrived he started demanding 20,000.
“Long ride… Long ride…” he said. I told him we had already agreed, but unfortunately I didn’t have a 5,000 VND bill, and he said he didn’t either. So I gave him a 10,000 VND bill and then went to split a 10,000 VND bill at the hostel.
One more thing I must say is that bargaining culture is ingrained in Asia. Don’t think at all that it is impolite to cut the price or to stand behind the price you agreed to. The touts know how to bargain even better than tourists. When the motorbike driver asked for 20,000 after agreeing to 15,000, he was using a trick of bargaining to try to earn more. At the very least, there need not be any value judgment about bargaining, but, if you must make a value judgment out of it—if you must consider whether or not you are being stingy—then consider the other side as well. Someone who asks for an inflated price—often on the basis of your perceived nationality—is being more impolite.