Question about relationship between turn out speed, control and indication.

[ericyang_thx]

Dear Sirs,

I would to ask how turnout speed affect which turnout indicator and special control should be chosen for the layout.

I just think that junction indicator is for the route with similar line speed after a turnout; standard indicator is for the route with slow line speed (less than 40 m.p.h/65 km/h) after a turnout or a turnout right after a start signal from a platform; and miniature indicator is for shunt or call-on route.

And when the turnout speed is around 100 km/h, MAF control should be provided; when the turnout speed is around 40 km/h, MAR or MAY-FA control should be provided; DEL control should be provided for shunt route.

Are these assumption correct or I just get confused?

Thank you, Best regards.

[REMBrum]

Hi,

In UK main line signalling:

Main Aspect Free (MAF) can be used when the diverging speed of the junction is within 10mph of the straight line speed, ie if the line speed is 80 and the divergence is 75, MAF could be applied.

Main Approach Yellow Flashing Aspect (MAY-FA) firstly requires a diverging speed to exceed 10mph below that of the straight line speed. MAY-FA is not permitted below 40mph. With a permissible approach speed of 80-125mph, the divergence speed can be 40mph or greater, but nothing below that. A lot of the divergences you will see on the IRSE exam layouts appear to be 40km/h and therefore not compatible with this junction control principle, however in some instances a 100km/h divergence is specified and this may point you to considering whether MAY-FA is appropriate.

Main Approach Release requires a diverging speed to exceed 10mph below that of the straight line speed, so will fit most circumstances, but is more operationally restrictive than MAY-FA and therefore will affect overall headways.

Would recommend reading RIS0703 for more reference: https://www.rssb.co.uk/rgs/standards/RIS...ss%201.pdf

[ericyang_thx]

Hi,

In UK main line signalling:

Main Aspect Free (MAF) can be used when the diverging speed of the junction is within 10mph of the straight line speed, ie if the line speed is 80 and the divergence is 75, MAF could be applied.

Main Approach Yellow Flashing Aspect (MAY-FA) firstly requires a diverging speed to exceed 10mph below that of the straight line speed. MAY-FA is not permitted below 40mph. With a permissible approach speed of 80-125mph, the divergence speed can be 40mph or greater, but nothing below that. A lot of the divergences you will see on the IRSE exam layouts appear to be 40km/h and therefore not compatible with this junction control principle, however in some instances a 100km/h divergence is specified and this may point you to considering whether MAY-FA is appropriate.

Main Approach Release requires a diverging speed to exceed 10mph below that of the straight line speed, so will fit most circumstances, but is more operationally restrictive than MAY-FA and therefore will affect overall headways.

Would recommend reading RIS0703 for more reference: https://www.rssb.co.uk/rgs/standards/RIS...ss%201.pdf

Dear Sir,

Thank you for your reply, it seems that my concepts is confused.

I would like to know more about indicator for turnout. As turnout speed is as low as 40km/h, does route indicator (or multi-lamp indicator, standard indicator) is more suitable for the scene instead of junction indicator?

Thank you, best regards