LIMITATIONS OF 3 ASP. SIGNALLING | 4 ASP. SIGNALLING HEADWAY

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LIMITATIONS OF 3 ASP. SIGNALLING

* IF S ≤ DGR/2 ≤ 1.5S (OR 2S ≤ DGR ≤ 3S), THE USABLE RANGE IS LIMITED BY: ‘DGR/2’ AT ITS UPPER END & ‘S’ AT ITS LOWER END AS CAN BE SEEN BELOW.

IF ‘DGR/2’ < ‘S’ (OR ‘DGR’ < ‘2S’), THERE IS NO OVERLAP OF THE BANDS AS CAN BE SEEN BELOW

 

* IT MEANS: 3ASP. SIGNALLING IS NOT ABLE TO RUN THE SERVICE.

*  SO 4 ASP. SIGNALLING SHALL BE EXAMINED IF IT CAN RUN THE REQUIRED SERVICE

4 ASP. SIGNALLING HEADWAY

* IN 4 ASP. SIGNALLING ALSO, ALL SIGNALS ARE IDENTICAL STOP SIGNALS.

* EACH SIGNAL DISPLAYS A SINGLE YELLOW ASPECT WHEN NEXT STOP SIGNAL IS AT RED.

* IT DISPLAYS DOUBLE YELLOW (FIRST CAUTION) ASPECT WHEN ITS NEXT TO THE NEXT SIGNAL IS AT RED.

 

* IT MEANS: THE SAFETY REQUIREMENT IS NOW MET BY TWO 4 ASP. SIGNAL SEPARATIONS OF ‘D4’.

* FOR SAFETY, S ≤ 2D4 ≤ 1.5S (OR 0.5S ≤ D4 ≤ 0.75S) &

* FOR SERVICE REQUIREMENTS, THE NEXT 4 ASP. SIGNAL ON APPROCH TO DOUBLE YELLOW CAN SHOW GREEN WHICH MEANS: FOR SERVICE, D4 ≤ DGR/3

 

SAFETY & SERVICE COMPATIBILITY IN 4 ASP. SIGNALLING

* IF DGR/3 > 0.75S, THE SERVICE BAND EXTENDS TO THE RIGHT OF THE SAFETY BAND AND THE ENTIRE SAFETY BAND REPRESENTS THE USABLE RANGE.

SAFETY & SERVICE COMPATIBILITY IN 4 ASP. SIGNALLING

 

 

* IF 0.5S ≤ DGR/3 ≤ 0.75S (OR 1.5S ≤ DGR ≤ 2.25S), THE USABLE RANGE IS LIMITED BY: DGR/3 AT ITS UPPER END & 0.5S AT ITS LOWER END, AS CAN BE SEEN ABOVE.

 

 

 

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