\begin{tikzpicture}[x=1cm,y=1cm,font=\small,>=Latex,
 v/.style={circle,fill=black,inner sep=1.8pt},
 landmark/.style={circle,fill=orange!85!black,inner sep=2.5pt},
 route/.style={blue!75!black,thick},
 other/.style={black!65,densely dashed,thick}]
\begin{scope}[shift={(.3,5.7)}]
\node[above=17pt] at (3.05,0) {(a) \(t<a\)};
\draw[black!40] (0,0)--(6.1,0);
\node[v,label=above:\(i\),label=below:\(0\)] at (0,0) {};
\node[v,label=above:\(j\),label=below:\(L\)] at (6.1,0) {};
\node[landmark,label=above:\(x_{ij}(t)\),label=below:\(t\)] at (1.35,0) {};
\fill (3.15,0) circle (1.5pt) (4.15,0) circle (1.5pt);
\draw[blue!85!black,line width=2.4pt] (3.15,0)--(4.15,0)
 node[midway,above=3pt] {\(e\)};
\node[below=3pt] at (3.15,0) {\(a\)};
\node[below=3pt] at (4.15,0) {\(a+1\)};
\draw[decorate,decoration={brace,mirror,amplitude=5pt}]
 (1.35,-.55)--(3.15,-.55) node[midway,below=7pt] {\(a-t\)};
\end{scope}
\begin{scope}[shift={(8.05,5.7)}]
\node[above=17pt] at (3.0,0) {(b) \(t>a+1\)};
\draw[black!40] (0,0)--(5.85,0);
\node[v,label=above:\(i\),label=below:\(0\)] at (0,0) {};
\node[v,label=above:\(j\),label=below:\(L\)] at (5.85,0) {};
\fill (1.45,0) circle (1.5pt) (2.45,0) circle (1.5pt);
\draw[blue!85!black,line width=2.4pt] (1.45,0)--(2.45,0)
 node[midway,above=3pt] {\(e\)};
\node[below=3pt] at (1.45,0) {\(a\)};
\node[below=3pt] at (2.45,0) {\(a+1\)};
\node[landmark,label=above:\(x_{ij}(t)\),label=below:\(t\)] at (4.1,0) {};
\draw[decorate,decoration={brace,mirror,amplitude=5pt}]
 (2.45,-.55)--(4.1,-.55) node[midway,below=7pt] {\(t-(a+1)\)};
\end{scope}
\end{tikzpicture}