On weekdays, you can expect a very heavy traffic from 6:45AM to 9AM in the morning, 10:45AM - 12:00PM at noon, 1:30PM to 2:30PM and again 4:45PM to 6:30PM. On weekend, commuting is less troublesome, but expect a flock of vehicles around major attractions and parks in the evening (5PM till 8PM) as many locals pour for their weekend.

A different situation exists on main holidays i.e. Khmer New Year (usually mid April), Water Festival (mid November), last three days of Pchum Ben Days (mid to late October, based on lunar calendar) and Chinese New Year Day (late January or early to mid February). If you stay in the capital Phnom Penh during these days, chance is you will encounter a crowded national roads to province as many of Phnom Penh-ers leaves the city for their hometown. It is very quiet in the capital, while in contrary, very busy in the provinces.

Well, there is barely any sidewalk in the capital. You will need to walk on street most of the time, which does not sound like safe. Locals tend to pave their sidewalk with different levels, so if you are on wheelchair, please do not use sidewalk. However, it's very fun walking in the evening and especially around major attractions and parks. A good shoes will help you walk easier. You are not supposed to walk after 9PM and also to any dark alley.

Motortaxi is a common sight in Phnom Penh. They will negotiate the price with you. Motortaxi does not operate on kilometers basis, so get your bargain skill going. If you go from point A to point B in central Phnom Penh, price is never above 2$. As motodup is unregulated, there are some scammers around, but it's not common. They speak little, yet understandable English. Some of them could not read map, therefore if you need to go somewhere, just tell them the nearest (<200meters) landmark in the area. If you need one, just shout "Motodup" /moto.doup/, but for most of the time, they will simply call for you if you look like you need a ride.

Probably the most recommended way to get around the city, tuk tuk is convenient and quite cheap-just a little more expensive than motodup. Just don't forget your wallet or bag. There are just too many news of foreigners forgetting their bags on Tuk Tuk. Speaking of which, also be vigilant with your belongings since there could be snatchers along the road. Tuk Tuk drivers speaks English. Most of them could read maps. They could also be hired for a full day tour for as little as 15$/day according to where you want to go during the day. Tuk Tuk scammers are not common. Anyway, they could take you to the hotels where they will get the commission. It's totally yours to decide whether to take the deal or not. Also, it is recommended to write down the price in number when you negotiate, so there is no miscommunication between both of you.

UPDATE: We now have the Tuk Tuk Meter. Yes! It's the "metered" type. You put point A to point B and they will charge your money based on the distance. It's an LPG-powered three-wheeler. It's more like Uber, but with a three-wheel tuk tuk twist.It costs 3000KHR for the first kilometer and 360KHR per 300 meters. They even have an app. Check their Facebook here: https://www.facebook.com/ezgo24h/about

A very comfortable way to travel in the city, it lacks the agility. You can call a toll-free number and get them pick you up from your hotel. Don't expect to flag one on the road since you might not find one down your road. There are couples of taxi operators, mainly run by Chinese company. Most of them are metered taxi, while the rest are airport taxis. Airport taxi usually takes you anywhere in Phnom Penh from the airport for less than 15$. Metered taxi could be identified by its big "METERED" sign on the car. It is not recommended to take taxi to get out to the province.

Global Taxi, the white cab (toll-free 1800 211888) and Choice Tax (yeah, yellow cab) are the ones with most presence here.

There are currently three lines of public bus operating from 7AM to 7PM everyday. It's not punctual though. You could wait as long as 30 minutes for a bus to come up. The price is 1500KHR per trip. The seating is quite comfortable.
Click below for larger version.

If you're the kind of adventurous type, take it. Wear helmet or buckle up. Beware of the people who run over the traffic lights and everything on the road.

But, if you're the type of conservative, don't do it. Let locals drive you. It's much safer.

Bicycling, on the other hand, is quite good, probably due to its slower speed. You can rent it for as low as 1$ per day. However, if you plan to stay long, it's better you buy one so you could sell it back for a decent percentage of your original price.

How is your experience? Let me know in the comment.