204 POWER DISTRIBUTION FOR ELECTRIC RAILROADS. 
frequent. 'These sizes give more room for the larger 
motors required and are better adapted for the cars. 
As to track, careful laying and good ballasting are 
the essential points. The rails themselves are what would 
be used for a light steam railroad, forty to sixty pound T 
being the rule, although at the termini the usual girder 
rails often have to be employed. It should be remembered 
that a city track gets far more wear and tear than the 
average interurban track and must be, accordingly, even 
more substantial. 
The rather infrequent stops in interurban work pro- 
duce on the whole a tendency toward uniform distribution 
of load that operates favorably on the necessary distribu- 
tion of power. The service is less liable to blockades, it 
is easier to hold to a regular schedule and there is less of 
the troublesome shifting of the load, than in street railway 
practice. Consequently it is somewhat easier to plan the 
feeder system. : 
On the other hand, the average distance to which 
power has to be transmitted is considerable, so that the 
aggregate amount of feeder copper is great, and it is ag- 
gravated by the frequent attempts to transmit power un- 
reasonably long distances at 500 volts to avoid distributed 
stations or other appropriate methods. 
The absolute amount of power required per car is, for 
an approximation, nearly double that required for a stand- 
ard double truck car in street railway work. The speed 
of the interurban car is nearly double, and the car itself is 
often heavier. On the other hand the average live load is 
likely to be smaller and the power wasted in stopping and 
starting is less. On the ordinary urban railway twenty 
to twenty-five amperes per car is not far from the aver- 
age power required through the day; on a busy interurban 
line forty to forty-five are likely to be required, or thirty 
to forty if the traffic be moderate. 
Consequently heavier motors are often employed than 
on street railways, although for many cases they are un- 
necessary. If the trafficis likely to be large or if the speed 
  
     
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
     
   
  
  
  
  
    
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