(CNN) -- International aid workers scrambling to get into Haiti face a series of obstacles, from an airport that is already overwhelmed to blocked roads and a lack of communication, electricity, food and water. 

And, as if that weren't enough, they will encounter a serious crime problem, a veteran disaster relief specialist told CNN. 

"Security now in this particular crisis has already been raised as a major, major issue," said Paul Sherlock, a senior humanitarian representative for Oxfam. 

"If you'd been in Haiti 25 years ago, even in Papa Doc's time, it was a pretty nasty dictatorship, and lots of people were killed. But infrastructure and services worked better then than they do now," he said. 

Francois "Papa Doc" Duvalier was president from 1957 to 1971. 

"It was safer to use public transport then than it was last year, certainly in terms of crime," he said. 

"Over the last 10, 15, 20 years, the gangs and the drug culture have taken hold of Haiti, and that is why over the last four to five years, the United Nations has been trying to administer security in the capital and all the provincial cities as well," he said. 

Nongovernmental organization workers "have not been using public transport or taxis because of the security risk they face. International aid workers certainly didn't." 

Aid workers on their way to Haiti now are not sure how to ensure their safety, he said. 

Some are "probably using U.N. military as escorts, but many NGOs are uncomfortable using any military escort. They have been going to the police, but I don't know, after what has happened, whether the police are in any better position to provide it." 
What are they up against?
a series of obstacles