Example showing how to use natbib's \defcitealias to shorten or alter BibTeX citations.

shortCite.bib

@techreport{caltrans2002,
    	Author = {{California Department of Transportation}},
    	Title = {{Humboldt Bay Bridges Seismic Substructure Retrofit Environmental  Assessment/Finding of No Significant Impact (EA/FONSI)}},
    	Year = {2002}}

shortCite.tex

% !TEX TS-program = pdflatex
% !TEX encoding = UTF-8 Unicode
\documentclass[11pt]{article} 

\usepackage{natbib}
\bibliographystyle{plainnat}
\defcitealias{caltrans2002}{\scshape CalTrans, 2002}

\usepackage[tightpage,psfixbb]{preview}
\setlength{\PreviewBorder}{1ex}


\setlength{\parindent}{0em}

\begin{document}


% Without using a citealias
Lorem ipsum dolor sit amet, consectetur adipiscing elit \citep{caltrans2002}.

\bigskip

%Using a citealias
Lorem ipsum dolor sit amet, consectetur adipiscing elit \citepalias{caltrans2002}.
\bibliography{shortCite}

\end{document}