How to get my graph draw larger?

You can adjust it in the options for standalone, by changing the first line of your code to:

\documentclass[tikz,border={0 0 5pt 0}]{standalone}

Just as of topic supplement to Jānis Lazovskis answer with small changes of your code and his image border proposition. Changes are indicated in code by % <---.

Edit: table mydata is moved insidetikzpicture` and a little bit changed

\documentclass[margin=1pt]{standalone} % <---
\usepackage{pgfplots}
\pgfplotsset{compat=1.16}              % <---

\begin{document}
        \begin{tikzpicture}
    \pgfplotstableread{
interval  carT  carD
    1    1.2    0.1
    2    12.8   3.8
    3    15.5  10.4
    4    14.0  17.3
    5    7.9   21.1
    6    3.0   22.3
    7    3.0   22.3
    8    3.0   22.3
    9    3.0   22.3
   10    3.0   22.3
        }\mydata

    \begin{axis}[
    width=\linewidth,
    height=.8\linewidth,
    ybar=0.5mm,         % <--- distance between bars (shift bar)
    bar width=4.4mm,    % <--- width of bars
    legend style={legend columns=-1,
      outer sep=1mm,    % <---
      font=\scriptsize, % <---
      anchor=north,
      at={(0.5,1)},
                  },
    nodes near coords,
    nodes near coords style={font=\scriptsize, inner sep=2pt}, % <---
    nodes near coords align={vertical},
    ylabel={\%},
    ymin=0, ymax=30,     % <---              
    xtick=data,
    scale only axis,     % <---
        ]
    \addplot table[x=interval,y=carT]{\mydata};
    \addplot table[x=interval,y=carD]{\mydata};
    \legend{Trips, Distance}
    \end{axis}
\end{tikzpicture}
\end{document}