The U.K. continues to lead European markets in Travel category penetration at 66.5 percent, up 8percentage points from a year ago. Ireland and Spain show similarly high penetration rates, with 58.7 percent reach and 57.3 percent reach, respectively. Although Russia currently has the lowest penetration rate for Travel properties among the eighteen markets at 27.8 percent, it showed the highest growth in unique visitors over the past year with a 41 percent increase. Expedia Inc., which includes TripAdvisor Sites, Expedia Sites, and Sites, attracted the most unique visitors in April 2011 with 21.7 million. Inc. followed with 16.4 million unique visitors, up 10 percent versus last year – the highest growth rate among the top Travel properties in Europe. Priceline’s sizeable audience was fueled in large part by hotel reservation site, which attracted 15.8 million visitors. Groupe SNCF (French National Railway Corporation) was the third most heavily visited property in April with 9.3 million visitors. Get the full story at comScore