Tweening in order

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4

Specifying the EasingStyle as Linear will ensure that the tweened instance moves at a consistent rate.

Adding it into your implementation:

local TweenService = game:GetService("TweenService") -- appropriate convention is to declare services exactly as they are in the datamodel.

Info = TweenInfo.new(
    15,
    Enum.EasingStyle.Linear
)

function start()
    for i,v in pairs(workspace.Track:GetChildren()) do
        local tween = TweenService:Create(script.Parent, Info, {CFrame = v.CFrame})
        tween:Play()
        tween.Completed:Wait() -- yields until the tween is completed.
    end
end

start()