src/models/car.xml

<mujoco>
  <compiler autolimits="true"/>

  <asset>
    <texture name="grid" type="2d" builtin="checker" width="512" height="512" rgb1=".1 .2 .3" rgb2=".2 .3 .4"/>
    <material name="grid" texture="grid" texrepeat="1 1" texuniform="true" reflectance=".2"/>
    <mesh name="chasis" scale=".01 .006 .0015"
      vertex=" 9   2   0
              -10  10  10
               9  -2   0
               10  3  -10
               10 -3  -10
              -8   10 -10
              -10 -10  10
              -8  -10 -10
              -5   0   20"/>
  </asset>

  <default>
    <joint damping=".03" actuatorfrcrange="-0.5 0.5"/>
    <default class="wheel">
      <geom type="cylinder" size=".03 .01" rgba=".5 .5 1 1"/>
    </default>
    <default class="decor">
      <site type="box" rgba=".5 1 .5 1"/>
    </default>
  </default>

  <worldbody>
    <geom type="plane" size="3 3 .01" material="grid"/>
    <body name="car" pos="0 0 .03">
      <freejoint/>
      <light name="top light" pos="0 0 2" mode="trackcom" diffuse=".4 .4 .4"/>
      <geom name="chasis" type="mesh" mesh="chasis"/>
      <geom name="front wheel" pos=".08 0 -.015" type="sphere" size=".015" condim="1" priority="1"/>
      <light name="front light" pos=".1 0 .02" dir="2 0 -1" diffuse="1 1 1"/>
      <body name="left wheel" pos="-.07 .06 0" zaxis="0 1 0">
        <joint name="left"/>
        <geom class="wheel"/>
        <site class="decor" size=".006 .025 .012"/>
        <site class="decor" size=".025 .006 .012"/>
      </body>
      <body name="right wheel" pos="-.07 -.06 0" zaxis="0 1 0">
        <joint name="right"/>
        <geom class="wheel"/>
        <site class="decor" size=".006 .025 .012"/>
        <site class="decor" size=".025 .006 .012"/>
      </body>
    </body>
  </worldbody>

  <tendon>
    <fixed name="forward">
      <joint joint="left" coef=".5"/>
      <joint joint="right" coef=".5"/>
    </fixed>
    <fixed name="turn">
      <joint joint="left" coef="-.5"/>
      <joint joint="right" coef=".5"/>
    </fixed>
  </tendon>

  <actuator>
    <motor name="forward" tendon="forward" ctrlrange="-1 1"/>
    <motor name="turn" tendon="turn" ctrlrange="-1 1"/>
  </actuator>

  <sensor>
    <jointactuatorfrc name="right" joint="right"/>
    <jointactuatorfrc name="left" joint="left"/>
  </sensor>
</mujoco>