why do pillars holding the track of metro trains have a broader base?

Dear Student, 
Please find below the solution to the asked query: 

• Pillars with broad base have more stability and stable equilibrium
•   Hence, pillars with broad base are preferred for stability

Hope this information will clear your doubts about Stability                      
If you have any more doubts just ask here on the forum and our experts will try to help you out as soon as possible.