Can a person legally be charged with a DUI after being stopped and then being allowed to drive themselves to another location about 500 feet on a main road to take a soberity test?

Driving under the influence (DUI), driving while intoxicated (DWI), drunken driving, drink driving, drunk driving, operating under the influence, drinking and driving, or impaired driving is the crime of driving a motor vehicle with blood levels of alcohol in excess of a legal limit ("blood alcohol content", or "BAC"). Similar regulations cover driving or operating certain types of machinery while affected by drinking alcohol or taking other drugs, including, but not limited to prescription drugs. This is a criminal offense in most nations. Convictions do not necessarily involve actual driving of the vehicle.

In most jurisdictions, a quantitative measurement such as a blood alcohol content (BAC) in excess of a specific threshold level, such as 0.05% or 0.08%, defines the offense with no need to prove impairment or intoxication. In some jurisdictions, there is an aggravated category of the offense at a higher BAC level, such as 0.12%. In most countries, anyone who is convicted of injuring or killing someone while under the influence of alcohol or drugs can be heavily fined, as in France, in addition to being given a lengthy prison sentence. Many employers or occupations have their own rules and BAC limits; for example, the United States Federal Railroad Administration has a 0.04% limit for train crew. Certain large corporations have their own rules; for example, Union Pacific Railroad has their own BAC limit of 0.02% that, if violated during a random test or a for-cause test — for example, after a traffic accident — can result in termination of employment with no chance of future re-hire. Some jurisdictions have multiple levels of BAC for different categories of drivers; for example, the state of California has a general 0.08% BAC limit, a lower limit of 0.04% for commercial operators, and a limit of 0.01% for drivers who are under 21 or on probation for previous DUI offenses.

Based upon what you have written, you can be legally charged with a DUI offense. I suggest that you consult with a criminal defense attorney in your locality. One can be found on attorneypages.com.