Houston to Galveston even during construction , contracts provide for all of time there are 6 lanes open , 3 on each side plus frontage access roads. The times, which are infrequent, are when main lanes are closed , like when major over passes are being demolished necessitating closures. Alternative routes are always provided by contract . Saturday mornings are free sailing unless a major wreck occurs , which can happen anywhere in the world . Don't overthink this . We travel back and forth between Galveston Houston often and rarely experience major stoppages. It can happen with extenuating circumstances.