Las Vegas business and civic leaders are seeing more frequent traffic snarls that frustrate visitors who drive into the city to enjoy its many gaming and entertainment attractions. There’s concern that Vegas may soon lose many of those visitors and the income the city derives from them because of the massive traffic jams. Now a company wants to help solve the problem by bringing in visitors on a speedy climate-friendly rail line with amenities like free internet. But some see risks in such a privately financed intercity passenger rail system with a high price tag.  Fulton Schools Professor Steven Polzin, a civil engineer who has experience as a U.S. Department of Transportation adviser, cautions that it could be a fine line between whether such a system will become an asset or a drag on the cities’ financial outlook.