The sight lines on entering an entrance on a local road

341power

Hi,

I am looking for information on forward and stopping visibility requirements for a new entrance on a local road with a speed limit of 80 km.

Forward and rear visibility for a car waiting to turn in can be seen from a safe distance by a car approaching from the rear or in front.

I woul be greatfull if some one could help, Thank You

BryanF

What sight line distances were requested? Your local arch/eng will be used to these requirements. I've seen 160 requested, but arguments made for less. Often a deal with a removal of a neighbouring ditch can be a solution

341power

BryanF wrote: »

What sight line distances were requested? Your local arch/eng will be used to these requirements. I've seen 160 requested, but arguments made for less. Often a deal with a removal of a neighbouring ditch can be a solution

I have tried to contact the council but they have not return me calls, that is why I have put a post up.

The sight lines on exiting the site are 90 meters in both directions. What I would like to know is the sight lines required for entering the site. 160 meters sounds like a lot for a entrance that needs 90 meter on exiting.

sydthebeat

it depends on the classification of the particular road

ie local, regional, national primary, national secondary, strategic etc

the sight line triangle is from the centre (either 3.0m or 2.4 m back, depending on the local authority) of the entrance to the near side of the carriageway.
Sight lines for 'turning in' to a site are generally covered by the above sightline triangle, once the horizontal alignment of the road doesnt pose a problem.

341power

sydthebeat wrote: »

it depends on the classification of the particular road

ie local, regional, national primary, national secondary, strategic etc

the sight line triangle is from the centre (either 3.0m or 2.4 m back, depending on the local authority) of the entrance to the near side of the carriageway.
Sight lines for 'turning in' to a site are generally covered by the above sightline triangle, once the horizontal alignment of the road doesnt pose a problem.

Hi, thanks for your reply.
The new entrance is located on a local road the speed limit is 80 km, set back is 2.4, sight line distances are 90 meters. I want to know what distance for the unobstructed visibility for a stationary right turning vehicle is. Is the correct distance 90 meters? Or is it more?

Metric Tensor

I think this is the link you are probably looking for OP:
http://www.tiipublications.ie/library/DN-GEO-03031-06.pdf

Table 3 is probably what you are interested in:


Desirable Minimum Stopping Sight Distance for a road with a Design Speed of 70km/h is 120m ... steps down to 90m and 70m depending on circumstances. Bear in mind this is based on design speed not speed limit and 80km/h is not given as one of the design speeds although you'd imagine some form of interpolation might be possible.

If you can tell us the reason for your query we might be able to help you better.

sydthebeat

341power wrote: »

Hi, thanks for your reply.
The new entrance is located on a local road the speed limit is 80 km, set back is 2.4, sight line distances are 90 meters. I want to know what distance for the unobstructed visibility for a stationary right turning vehicle is. Is the correct distance 90 meters? Or is it more?

As this is a new entrance, the sight triangle requirement will cover the "turning in" movement. The sight triangle distances depends on the road classification.

Calahonda52

Metric Tensor wrote: »

I think this is the link you are probably looking for OP:
http://www.tiipublications.ie/library/DN-GEO-03031-06.pdf

Table 3 is probably what you are interested in:


Desirable Minimum Stopping Sight Distance for a road with a Design Speed of 70km/h is 120m ... steps down to 90m and 70m depending on circumstances. Bear in mind this is based on design speed not speed limit and 80km/h is not given as one of the design speeds although you'd imagine some form of interpolation might be possible.

If you can tell us the reason for your query we might be able to help you better.

MT,
Perhaps from Table 2
80 mandatory Speed limit gives a Max design speed of 85
which yields 160m, as suggested by BF

Metric Tensor

Calahonda52 wrote: »

MT,
Perhaps from Table 2
80 mandatory Speed limit gives a Max design speed of 85
which yields 160m, as suggested by BF

Well spotted CH.

341power

Calahonda52 wrote: »

MT,
Perhaps from Table 2
80 mandatory Speed limit gives a Max design speed of 85
which yields 160m, as suggested by BF

Hi thanks for your reply, the link to the NRA document has been very helpful. 160 meters will work in the case of the new entrance.

But how do you know what circumstances you can use 120 or 90 meters if the design speed is 85.

The reason for my query is a request of further information from the council I received. I would post a image of the site plan but boards will not let me as I'm a new user which would explain it a bit better.

Metric Tensor

In cases of planning it's pretty much at the council's discretion - so the only way that I can see that you can get the "step back" is if you put forward an argument that sufficiently convinces the council road engineer - this would not be easy!

If you think that all the cars passing on the road are travelling at a slower speed than 85 you could do a traffic survey (quite expensive) to actually get a measured value for the speed and then assuming this speed is lower use a lower design speed.

Calahonda52

341power wrote: »

But how do you know what circumstances you can use 120 or 90 meters if the design speed is 85.

.

I would not concern yourself too much with these ideas as nobody will sign off on less than 160, which is a minimum figure, for PI reasons, if no other.

What was the exact text of the RoFI question from the LA?

edit, was composing while MT posted...he explains it much better

341power

Calahonda52 wrote: »

I would not concern yourself too much with these ideas as nobody will sign off on less than 160, which is a minimum figure, for PI reasons, if no other.

What was the exact text of the RoFI question from the LA?

edit, was composing while MT posted...he explains it much better

The exact words are "forward and stopping visibility requirements to be satisfied".

I will ring the LA and go from there but from what you are saying the easiest option is to go with the 160 meters and make it work.

Thank you for your help and advice MT and Calahonda52.

Metric Tensor

Try to organise a meeting with the Roads Engineer who is looking at it. That way you'll know exactly what he/she wants when replying to the FI.