\documentclass[border=1bp,varwidth]{standalone}
\usepackage{tikz,fp}
\usetikzlibrary{calc}

\makeatletter
\def\calcLength(#1,#2)#3{%
\pgfpointdiff{\pgfpointanchor{#1}{center}}%
             {\pgfpointanchor{#2}{center}}%
\pgf@xa=\pgf@x%
\pgf@ya=\pgf@y%
\FPeval\@temp@a{\pgfmath@tonumber{\pgf@xa}}%
\FPeval\@temp@b{\pgfmath@tonumber{\pgf@ya}}%
\FPeval\@temp@sum{(\@temp@a*\@temp@a+\@temp@b*\@temp@b)}%
\FProot{\FPMathLen}{\@temp@sum}{2}%
\FPround\FPMathLen\FPMathLen5\relax
\global\expandafter\edef\csname #3\endcsname{\FPMathLen}
}
\makeatother

\def\centerarc[#1](#2)(#3:#4:#5)% Syntax: [draw options] (center) (initial angle:final angle:radius)
    { \draw[#1] ($(#2)+({#5*cos(#3)},{#5*sin(#3)})$) arc (#3:#4:#5) }

\begin{document}

\begin{tikzpicture} [scale=1.5,font=\small] %modify these options at will
\coordinate (O) at (3,0); %some point on the right
\node [draw,fill=gray!30,thick, minimum width=1cm, minimum height=2cm, anchor=south,yshift=-0.25 pt] (car) {};
\coordinate (R) at (car.north);
\coordinate (Ti) at ($(R)+(0,1.25)$);
\def\ptRadius{1.25pt}
\calcLength(O,R){Rdist}
\calcLength(O,Ti){Ddist}
%as the results from tikz come in points but cms are used in nodes, you need the following.
\def\locScale{28.45274} %scale of cm to points in tikz nodes :-(((
%See the reasons here: https://tex.stackexchange.com/questions/325969/converting-a-tikz-length-into-a-tex-length


\coordinate (Tf) at ($(O)+(153:\Ddist/\locScale)$);

\draw [fill] (O) circle (\ptRadius) node [above] {$O$};
\draw (O) -- (0,0);
\draw (O) -- node [above, midway] () {$R$} (car.north);
\draw (O) -- node [above, midway] () {$D$} (Ti);



\centerarc[densely dotted, ->, >=stealth](O)(160:120:\Rdist/\locScale) node [right] () {$P_{car}$};
\centerarc[densely dotted, ->, >=stealth](O)(128:160:\Ddist/\locScale) node [below] () {$P_{target}$};

\draw [red] (R) -- node [right,midway, black] {$x$} (Ti);
\draw [red] (R) -- (Tf);

\draw [fill,red] (Ti) circle (\ptRadius) node [above left,black] {$T_i$};
\draw [fill,red] (Tf) circle (\ptRadius) node [above left,black] {$T_f$};


\end{tikzpicture}

\end{document}