How to read the xml node and replace other node in ruby

I have a below xml. I need to read the node Bus and replace Transport to ROAD WAYS and Flight to Air Ways

 <Field>
  <Name>Bus</Name>
  <Value>Volvo</Value>
  <Desc>Transport</Desc>
</Field>
<Field>
  <Name>Flight</Name>
  <Value>Air-Bus</Value>
  <Desc>Transport</Desc>
</Field>