The　emergence　of　communication-based　train　control　(CBTC)　system　within　urban　rail　transport　has　improved　the　efficiency　of　safe　train　operations.　At　the　same　time,　the　CBTC　system　enhances　the　reliability　of　the　train　system　and　lowers　latency.　Nevertheless,　there　are　still　certain　critical　issues　that　need　to　be　considered　in　the　CBTC:　1)　limited　coverage　and　high　maintenance　costs　of　wayside　equipment;　2)　multiple　ground　devices　configuration　and　complex　system　architecture;　and　3)　insufficient　computing　capacity　of　the　train　leads　to　heavy　latency　and　energy　consumption.　The　multi-hop　ad　hoc　network　coexisting　with　train-to-train　communication　and　train-to-wayside　communication　is　applied　to　simplify　the　networking　architecture,　together　with　the　employment　of　mobile　edge　computing　(MEC)　servers　to　provide　massive　computing　and　communication　resources　for　trains.　Therefore,　in　this　paper,　a　new　multi-hop　ad　hoc　network　and　MEC-assisted　CBTC　framework　are　developed　for　computing　offloading　and　resource　allocation.　Offloading　decisions,　offloading　ratio,　computing　and　communication　resource　allocation　are　integrated　to　minimize　latency　and　energy　consumption.　Furthermore,　the　proposed　problem　is　a　mixed-integer　non-convex　problem　that　is　transformed　into　a　solvable　convex　problem,　and　the　consensus　alternating　direction　method　of　multipliers-based　(ADMM)　algorithm　is　employed　to　solve　the　problem.　The　simulation　results　show　that　our　proposed　method　has　remarkable　advantages　over　other　schemes.