LIMITATIONS OF 3 ASP. SIGNALLING

1. LIMITATIONS OF 3 ASP. SIGNALLING | 4 ASP. SIGNALLING HEADWAY:- 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

 

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

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

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

4 ASP. SIGNALLING HEADWAY

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

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

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

 

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

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

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

 

SAFETY & SERVICE COMPATIBILITY IN 4 ASP. SIGNALLING

1. 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.

 

 

2. 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.

 

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