<!ELEMENT stop (#PCDATA | time | coord)*>
<!ELEMENT vehicle_events (#PCDATA | stationary_vehicle | vehicle)*>
<!ELEMENT start (#PCDATA | time | coord)*>
<!ELEMENT time (#PCDATA)>
<!ATTLIST time units CDATA #IMPLIED>
<!ELEMENT stationary_vehicle (#PCDATA | size | coord)*>
<!ATTLIST stationary_vehicle id CDATA #IMPLIED>
<!ELEMENT vehicle (#PCDATA | size | start | stop)*>
<!ATTLIST vehicle id CDATA #IMPLIED>
<!ELEMENT y (#PCDATA)>
<!ELEMENT size (#PCDATA)>
<!ELEMENT coord (#PCDATA | x | y)*>
<!ATTLIST coord id CDATA #IMPLIED>
<!ELEMENT x (#PCDATA)>