High Quality Content by WIKIPEDIA articles! METRORail is the 7.5-mile (12.1 km) light rail line in Houston, Texas (USA). With an average weekday ridership of 36,250, METRORail ranks as the fourteenth most-traveled light rail system in the United States, with the second highest ridership per track mile. METRORail is operated by the Metropolitan Transit Authority of Harris County (METRO).