How to distinguish national roads from local/regional roads?

westnordost · 2018-07-04T19:17:44.000Z

For national primary and secondary roads, the default speed limit is 100 km/h.

For other rural (“local”/“regional”) roads, the default speed limit is 80 km/h.

Let’s say you turn into a rural road (from some driveway, but you know you are outside a built-up area). How do you know if you can drive 80 or 100 without having seen a speed limit sign? Can national roads be fundamentally distinguished from regional/local roads without looking at the ref sign (N… for national, R/L for regional/local)?

amapanda_ᚐᚋᚐᚅᚇᚐ · 2018-07-05T06:47:47.000Z

Hi. A better place to ask is the talk-ie mailing list, which is more active than the forum.

Unlike other European countries, Irish roads aren’t really split into rural/urban zones. In Germany you can see the official sign when a town/village begins, and one when you leave. And that has legal meaning for speed limits. Those signs showing the borders of a town/village don’t exist in Ireland. Speed limit signs are nearly always explicitly sign posted, I don’t think there’s a lot of “implicit” signs.

The highway tag will tell you whether it’s a national primary, national secondary etc. The ref will tell you as well. National roads are highway=trunk or highway=primary.

westnordost · 2018-07-05T08:47:08.000Z

So, national primary roads are always tagged as trunk and national secondary roads are always tagged as primary? From secondary downwards it is always a local/regional road?

Are all national primary roads motorroads? (tagged with motorroad=yes)?

Regarding built-up areas: Is there any way to identify if you are in an area where the urban speed limit would apply in the case no speed limit signs are visible? E.g. In GB, areas where the urban speed limit applies (“national restricted road”) will have street-lighting.

amapanda_ᚐᚋᚐᚅᚇᚐ · 2018-07-05T09:13:53.000Z

national primary roads are always tagged as trunk and national secondary roads are always tagged as primary? From secondary downwards it is always a local/regional road?

Yes, if not that’s a tagging mistake. ?

You may be interested in the Rules of the Road (275 page PDF!) which explains driving law. Section 8 (page 111 onwards) covers speed limits, but I don’t think it’s too helpful for this now.

Are all national primary roads motorroads? (tagged with motorroad=yes)?

I didn’t know about the motorroad tag. There are 57 instances of the motorroad tag in Ireland, the wiki tells me that highways that have motorway-like access restrictions (i.e. cyclists and pedestrians banned) but that are not a motorway. No, national primary roads are not “Motorroads”.

Regarding built-up areas: Is there any way to identify if you are in an area where the urban speed limit would apply in the case no speed limit signs are visible? E.g. In GB, areas where the urban speed limit applies (“national restricted road”) will have street-lighting.

I was wrong earlier. Apparently Irish law does have the concept of “built-up areas” (i.e. urban areas), where a slower speed limit (of 50 kmph) applies (cf. p 114 of RotR, Sec 5(1) of the Road Traffic Act 2004, and Local Government Act 2001). However these “towns”/“build up areas” aren’t marked with signs like they are in Germany.

But, In my experience nearly all speed limit changes are explicitly marked with a sign ( look at these 2 mapillary images (from opposite directions): #1, #2), so I don’t think you need to worry much about legal urban definitions. And I’m pretty sure most Irish people don’t know that exists. If you explain why you’re asking, maybe I can explain things? Is this for StreetComplete?

SK53 · 2018-07-05T15:33:31.000Z

As someone who has recently driven in Ireland, I concur with rorym’s comments.

Even in quite sparsely populated parts of the country main roads are likely to have regularly changing explicit speed limits: perhaps stepping through 50, 60, 80 and 100 kmh as one gets further from towns/villages. The 60 limit may apply for quite a distance from the a local centre (e.g., R238 from Moville to Greencastle is this speed most of the way, probably because it is well used by pedestrians even where there are no pavements). Additionally speed limits may drop for junctions and stretches of road with many curves.

Outside of main towns and cities, Ireland’s population is in general much more dispersed than one gets in the nucleated settlements familiar elsewhere in Western Europe, and this creates different needs in terms of speed limits. Furthermore as Ireland relatively recently moved from imperial to metric units for road signs, I would have expected that this transition was used as an opportunity to revisit some of the standards.

Certainly my impression driving on predominately secondary & tertiary roads in Monaghan, Cavan and Donegal was that speed limits change quite frequently and pure 100 kph sections of road are relatively rare for these road classes. (Note also that speed limit signs are one of the most obvious markers of the international boundary).

@rorym: the motorroad tags more or less exclusively refer to the West Link in Belfast. I’ve removed one approaching Moira as I know that one is completely spurious. I’d expect the one just N of Limerick is too. @westnordost: I think you can ignore motoroad in the Republic of Ireland, with the single Belfast case in Northern Ireland.

westnordost · 2018-07-05T21:48:56.000Z

Alright, thank you for the clarifications. I added the informations to that wiki page

VictorIE · 2022-08-29T01:13:52.000Z

Apologies for dragging up an old thread.

“Let’s say you turn into a rural road (from some driveway, but you know you are outside a built-up area). How do you know if you can drive 80 or 100 without having seen a speed limit sign?” - well, how did you get there? You will normally know what route you arrived on. If you don’t know, stick to 80 km/h until you see a speed limit sign or route number sign, which are quite frequent. All national routes are numbered N1-50 (M1-50 if a particular part is a motorway) and all the others are R101-999 or L1001-99999. National routes represent about 5% of the road network.

With the exception of motorways, note that Irish roads and in OSM throughout the world, categorises of roads are based on the route hierarchy - how to get from A to B, and NOT what the road looks like (width, dual carriageway, grade separation, hard shoulders, junctions, etc.). So you can have a minor route that is technically a dual carriageway ‘just because’ and a more important route that is only 5 metres wide.

Motorroads do exist in places, e.g. the Cork and Limerick tunnels and certain motorway-like roads. However, they simply ban pedestrians and cyclists (and potentially other categories), they are NOT a designated type of road. The use of motorroad=* has been disputed on OSM, with some users applying them to in conjunction with highway=trunk, which may or may not be correct. https://forum.openstreetmap.org/viewtopic.php?id=72572

Note that “default” speed limits are merely a legal starting point - there are thousands of pages of bye-law documents specifying different limits for specific roads. You can see them here: https://www.speedlimits.ie/adopted-current-bye-laws (some out of date) https://www.dublincity.ie/sites/default/files/2021-04/30kp-speed-limit-review-2020_map.pdf and https://dttassupportoffice.sharepoint.com/sites/DTTASSupportOffice/Speed%20Limits/Forms/AllItems.aspx?id=%2Fsites%2FDTTASSupportOffice%2FSpeed%20Limits%2FWebsite%20Documents%2FAdopted%20Bye%2Dlaws%2FSDCC%2FSpeed%2DLimit%2DBy%2DLaw%2DReview%2D2016%2DMar%2D10%2D2017%2Epdf&parent=%2Fsites%2FDTTASSupportOffice%2FSpeed%20Limits%2FWebsite%20Documents%2FAdopted%20Bye%2Dlaws%2FSDCC&p=true&ga=1 are useful, as they are mapped fully.