Fixing the size of ingredient in the tables' cells

Fixing the size of ingredient in the tables' cells

I have created a table as follows:
\documentclass{article}
\usepackage{array,booktabs}
\usepackage{colortbl}
\usepackage{xcolor}
\begin{document}
\newcolumntype{L}{@{}>{\kern\tabcolsep}l<{\kern\tabcolsep}}
\begin{table}[htp]
\caption{Indicators for sustainable transportation \citep{r2}}
\label{tab: ind}
\centering
\footnotesize\setlength{\tabcolsep}{2.5pt}
\begin{tabular}{@{} l L L L @{} >{\kern\tabcolsep}l @{}} \toprule
\emph{Objective} & \emph{Indicator} & \emph{Direction} &&& \\\midrule
\emph{Economic} & & & & \\
\rowcolor{black!3}[0pt][0pt] Transport diversity & Mode split: portion of
travel made by walking, cycling, rideshare, public transit and telework &
More is better \\
\emph{Social} & & & & \\
\rowcolor{black!6}[0pt][0pt] Health and fitness & Percentage of population
that regularly walks and cycles & More is better \\
\rowcolor{black!8}[0pt][0pt] Non-motorized transport planning & Degree to
which impacts on non-motorized transport are considered in transportation
modeling and planning & More is better \\
\emph{Environmental} & & & & \\
\rowcolor{black!10}[0pt][0pt] Resource efficiency & Non-renewable resource
consumption in the production and use of vehicles and transport facilities
& Less is better \\
\rowcolor{black!12}[0pt][0pt] Climate change emissions & Per capita fossil
fuel consumption, and emissions of CO2 and other climate change emissions
& Less is better \\
\rowcolor{black!14}[0pt][0pt] Noise pollution & Portion of population
exposed to high levels of traffic noise & Less is better \\
\bottomrule
\hline
\end{tabular}
\end{table}
\end{document}
And the output is presented as:

As you can see part of the table in out of the border. The problem is
caused because the cell's texts are long.
How can I fix it, automatically?