2850mm 

For Two girder RCC T beam bridge 

= Gsp / 2

= 5700 / 2

= 2850mm

1900mm

For Three girder RCC T beam bridge 

= Gsp / 2

= 3800 / 2

= 1900mm

1425mm 

For Four girder RCC T beam bridge 

= Gsp / 2

= 2850 / 2

= 1425mm