In Civil Engineering (railway Work), What is the distance between railway tracks?

Normal track =1435 mm.

Soviet-Union, Finland and Mongolia1520/1524 mm (1524 mm =60 inch).

In Spain and Portugal1668 mm.

Brazil, Ireland and Northern-Ireland1600 mm (63 inch).

India, Pakistan and the largest part of Argentina1676 mm.

Australia1067 mm (kaapspoor) and1600 mm.

In South Africa, Japan, South east-Asia, Indonesia and parts of South America1067 mm (42 inch;

Broad gauge railways use a track gauge (distance between the rails) greater than the standard gauge of1,435 mm (4 ft8 1⁄2 in).

Distance between railway track all the world1435 mm . so in Russia1522 mm

The Normal Distance is1435 for Railway track. i agreed with all experts. 

The most popular distance between railway tracks is 1435mm

see this link you will get the perfect information of distances in each country

http://en.wikipedia.org/wiki/Track_gauge

Distance btween railway tracks ismm (4ft/2 in )

As per my best knowledge in Railway industry four type of gauge . Or Distance between Railway tracks.

1- Broad gauge - 1676 mm 

2 - Standard Gauge - 1435 mm 

3 - Meter  Gauge - 1000 mm 

4- Narrow Gauge -763 mm /610 mm 

for metro systems the gauge is 1435mm. 

In Istanbul, all of the rail gauges are 1435mm. But there is some historical tramlines and they have 1000mm gauges

1435 mm is the standard gauge, distance between left & right rails. 

There are type of gauges which are being used like broad gauge, standard gauge and narrow gauge but many railways adapt the standard gauge which is 1.435meters.