Wie kann ich das genau formen?

Question

Ich versuche, das Auto als mein Referenzauto zu zeichnen. Aber es ist sehr schwierig. Ich komme nicht auf die richtige Idee und Lösung. Hier ist mein Referenzauto.

\documentclass{article}
\usepackage{tikz}
\usepackage{pst-plot}
\usepackage{pst-eucl}
\usepackage{amsthm}


\usepackage{environ}
\makeatletter
\newsavebox{\measure@tikzpicture}
\NewEnviron{scaletikzpicturetowidth}[1]{%
  \def\tikz@width{#1}%
  \def\tikzscale{1}\begin{lrbox}{\measure@tikzpicture}%
  \BODY
  \end{lrbox}%
  \pgfmathparse{#1/\wd\measure@tikzpicture}%
  \edef\tikzscale{\pgfmathresult}%
  \BODY
}
\makeatother

\makeatletter
\newcommand*\setupscalewithtikz[1][\linewidth]{%
\newsavebox{\box@tikzpicture}
\newlength{\newwidth}
\setlength{\newwidth}{#1} 
}
\NewEnviron{tikzpicture*}[1][]{%
  \begin{lrbox}{\box@tikzpicture}%
  \begin{tikzpicture}[#1]
     \BODY
  \end{tikzpicture}% 
  \end{lrbox}%
  \pgfmathsetmacro\width@scale@picture{\newwidth/\wd\box@tikzpicture}%
  \begin{tikzpicture}[#1,scale=\width@scale@picture]
    \BODY
  \end{tikzpicture}% 
}%
\makeatother

\begin{document}
  \begin{figure}
      %\centering
      \begin{center}
      \begin{scaletikzpicturetowidth}{.8\textwidth}
          \begin{tikzpicture}[scale=\tikzscale, declare function={
              excitation(\t,\w) = sin(\t*\w);
              noise = rnd - 0.5;
              source(\t) = excitation(\t,20) + noise;
              filter(\t) = 1 - abs(sin(mod(\t, 50)));
              speech(\t) = 1 + source(\t)*filter(\t);
            }]
            \draw
            [draw=black,rounded corners=6ex,very thick] (3.6,0.5) -- (1.5,.5) -- ++(0,2.5)-- ++(3,0);% --  ++(15,0) -- ++(0,-2.5)--++(-2.5,0);
            \draw[draw=black,rounded corners=5ex,very thick](14.1,3) -- (16.1,3) -- ++(0,-2.5) -- ++(-2.1,0);

            \draw[draw=black,rounded corners=1.2ex,very thick](6,0.5)--(11.6,0.5);

            \draw[very thick, rounded corners=5ex,thick]  (4.5,3) -- ++(2,2) -- ++(6.6,0) -- ++(1,-2);


            \draw [draw=black,very thick](6,.5) arc (0:180:12mm);
            \draw [draw=black,very thick](14,.5) arc (0:180:12mm);


        \end{tikzpicture}
        \end{scaletikzpicturetowidth}
      \end{center}

      \caption{Sensitivity analysis for cut Model of car}
      \label{fig:sens_1ncar}
  \end{figure}
\end{document}