Drag and drop the ytd in mods/x64e.rpf/levels/gta5/vehicles.rpf

NOTE: Due to the bus spawning in different colours, i have included a bus carvariations down below to ensure it only spawns in pure white 
so that you don't have to open your mod trainer (Simple Trainer/Menyoo etc.) to change the colour everytime you spawn it.
Copy the entire thing below and paste it inside mods/update/update.rpf/x64/data/carvariations.ymt
Remove the original bus text first inside your carvariations.ymt before pasting this inside.

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<?xml version="1.0" encoding="UTF-8"?>

<CVehicleModelInfoVariation>
  <variationData>
     <Item>
      <modelName>BUS</modelName>
      <colors>
        <Item>
          <indices content="char_array">
            134
            134
            0
            156
          </indices>
          <liveries>
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
            <Item value="false" />
          </liveries>
        </Item>
      </colors>
      <kits>
        <Item>0_default_modkit</Item>
      </kits>
      <windowsWithExposedEdges />
      <plateProbabilities>
        <Probabilities>
          <Item>
            <Name>Standard White</Name>
            <Value value="100" />
          </Item>
        </Probabilities>
      </plateProbabilities>
      <lightSettings value="0" />
      <sirenSettings value="0" />
    </Item>
  </variationData>
</CVehicleModelInfoVariation>