function Is_Valid = Valid(Ant_k, Routes)
    global Start_Node;
    global End_Node;
    global T_max;
    global Group_Size
    Is_Valid = true;
    
    for user = 1: Group_Size
        if length(Routes.Path{Ant_k,1,user}) < 2 
            Is_Valid = false;
            return
        elseif Routes.Path{Ant_k,1,user}(1,1) ~= Start_Node || Routes.Path{Ant_k,1,user}(1,end) ~= End_Node
            Is_Valid = false;
            return
        end
        Time = 0.0;
        for index = 1:length(Routes.Path(Ant_k,1,user)) - 1
            Time = Time + Distance(Routes.Path{Ant_k,1,user}(1,index), Routes.Path{Ant_k,1,user}(1,index+1));
        end
        if Time > T_max 
            Is_Valid = false;
            return
        end
    end
end