I just returned from Colombia , where I ran afoul of a creative (and inconvenient) traffic law birthed in Bogotá  and now spreading throughout South America  (including Costa Rica ), where traffic congestion is extreme.
The 'pico y placa'  (rush hour & license plate) law was first introduced in Bogotá in 2000 as a way of reducing traffic congestion. The concept is simple:
Private vehicles are banned entirely from city roads on certain days of the week and between certain hours according to the last digit of their license plate. The effort was deemed successful at reducing traffic jams, so Medellín  followed suit as did other Colombian cities, plus Caracas  (Venezuela), Quito  (Ecuador), and elsewhere.
Costa Rica first implemented a pico y placa limitation in 2005 for San José , when petrol prices prompted an effort to reduce petrol consumption. In July 2008 the law became permanent. Like many Costa Rican laws, however, it was tinkered with and changed twice within weeks of coming into effect.
Currently ALL private non-commercial vehicles are banned from metropolitan San José between the hours of 6am and 7pm, based on the last number of their vehicle license plate, as follows:
Monday: 1 & 2
Tuesday: 3 & 4
Wednesday: 5 & 6
Thursday: 7 & 8
Friday: 9 & 0
The government is considering extending the restrictions to cover other cities in Costa Rica.
Tourists are not exempt. However, exemptions are made for cars owned by handicapped persons, plus buses, taxis, and motorcycles.
Fines are currently 6,500 colones (about US$13), but violators of the law can supposedly be fined as often as they are pulled over in any given day. Count yourself lucky: in Bogotá the fine is US$142, and the car can be impounded.
"Er, what's that, officer?... I'm sorry, I don't speak Spanish!"
Now what's that about the need for more buses and taxis? or, better yet, a superb Metro bus system, like Bogotá's TransMilenio .
For further information about travel in Costa Rica, buy Moon Costa Rica 
If you're traveling only to San José and the Caribbean, buy Moon Spotlight Costa Rica's Caribbean Coast  pocket guide.
If you're traveling only to the beaches of Nicoya, buy Moon Spotlight Costa Rica's Nicoya Peninsula  pocket guide.
If you're traveling only to Arenal and/or Monteverde, buy Moon Spotlight Costa Rica's Arenal & Monteverde  pocket guide.
Disclosure: I occasionally accept free or discounted travel when it coincides with my editorial goals. However, my opinion is never for sale. The opinions you see in Cuba & Costa Rica Journal are my unbiased reflection of the good, the bad, and the ugly.
Copyright © Christopher P. Baker