Licensed sales for non-medical, recreational marijuana are to go on sale in Colorado in the United States.

The state-authorised dispensaries were gearing up to an anticipated rush of customers, with preparations made to open their doors to customers on Monday, ahead of the introduction of the law on New Year's Day.

Residents of Colorado, aged 21 years or older, would be able to buy up to one ounce of marijuana from a licensed retail store.

Out of state residents are limited to purchases of one-quarter ounce. The marijuana is for private use, and may not be consumed in a public space. Police will continue to enforce laws against driving under the influence of marijuana.

As in any prosperous business, the marijuana dispensaries intend to offer their customers a variety of cannabis, according to Marques Moore, chief executive of NMS America Store.

"The far side of the house, the retail, I mean, it's pretty much going up to the front so they can see the vast variety of strains we have available," Moore  said. 

"We usually keep around 20 strains on the shelf at time, and then eventually we have a back area of cultivation where we actually grow plants."

Backlog

Colorado and Washington became the first US states to legalise marijuana for recreational purposes last year following a voter-approved constitutional amendment in the November 2012 election.

Several hundred entrepreneurs have applied for marijuana licence, but a backlog of paperwork meant only a few dozen received their licences and would be ready to do business on January 1.

"I think a lot of folks are, we are all scrambling at this last minute and we are not sure which of our friends in the industry are going to be able to open and which ones won't," said Robin Hackett, a herbalist with the Botanicare 21+ dispensary.

Police in Colorado were prepared to arrest any recreational marijuana user who slides outside the new state law regarding usage of the drug.

Unlike the familiar test for the use of excessive alcohol in the bloodstream, there is no effective roadside test to detect marijuana usage.

If Colorado police suspect a driver under the influence of marijuana, they would be taken to the police station for a blood test. A driver who refuses the blood test is subject to arrest.

"For marijuana there is no breath test. It is a blood test or refusal," said Colorado state trooper Josh Moore.

Source: Al Jazeera and agencies