Zombie train / David Macinnis Gill.

Enhanced descriptions from Syndetics:

The Zombie Chasers meets The Goonies in David Macinnis Gill's middle grade debut about a group of tweens who ride out the zombie apocalypse on a cobbled-together train. Fans of Ty Drago's The Undertakers: Rise of the Corpses and Max Brallier's The Last Kids on Earth will lose themselves in this page-turning, spine-chilling, and sometimes goofy survival story.

Wyatt has been riding out the zombie apocalypse on his crew's cobbled-together train for what feels like forever. It's a hopeless journey, the train running a loop that covers thousands of miles across the western U.S. But when a mysterious girl arrives with stories of a so-called Nirvana and a potential cure for the zombie parasite, Wyatt must decide between searching for the cure and protecting those entrusted in his care.

David Macinnis Gill's Zombie Train is a compelling survival story full of action, suspense, and plenty of zombies. Filled with both harrowing and humorous moments, Zombie Train follows an eccentric cast of characters as they contend with a changing world and shifting loyalties and friendships, and as they fight to remain in control--of their lives and of the future.