<p>It depends actually a non-congested road can be considered non-rivalrous as when you drive there you don’t really reduce the enjoyment or marginal utility of other people driving them.</p>

<p>However, once the road is congested it becomes rivalrous. </p>

<p>Also note that even though many textbooks include public roads as public goods this is actually not technically correct. Technically since roads can be protected by toll booths they are excludable so it’s not correct to categorize them as public goods, they are actually a separate category of quasi-public goods - that is goods that have many characteristics of public goods but also some characteristics of private goods.</p>

<p>However, it’s very hard to find proper example of pure public goods (although army is a good example, non-polluted air another), so often undergraduate textbooks that are less nuanced than graduate textbooks include quasi-public goods that are very close to public good in same category.</p>

CC BY-SA 4.0
2020-04-27T01:51:48.290Z
Makes sense. However on non-polluted air being a pure public good, couldn't you say the more people there are, the less oxygen would be available for everyone else?! Specifically, given average O2 consumption of a human, there exist some number of humans where the global rate of oxygen consumption would be more than the rate of its production?
Atonal
CC BY-SA 4.0
2020-04-27T01:56:23.813Z
@Atonal yes it’s always all about context there is no worry that we ever run out of O2 at any realistic human population growth. Of course O2 at the international space station is neither non-rivalrous nor non-excludable. Same under water. However, on earth at and above sea level it’s one of the best example of pure public goods.
1muflon1
CC BY-SA 4.0
2020-04-28T07:08:54.503Z
@1muflon1 I don't think your examples of pure public goods really hold. Because everything is quasi-public. You can totally have an army that only serves/protects one person/one group of people. That would be similar to the toll booth. Same goes with the non-polluted air. Air pollution makes the non-polluted air rivalrous (if I pollute air, it is not non-polluted for you any more) and then having e.g. fine-dust filters in your buildings gives you non-public clean air.
Dakkaron
CC BY-SA 4.0
2020-04-28T07:10:54.323Z
If you think the last statement is exaggerated, have a look at how things are handled in heavily polluted cities around the world.
Dakkaron
CC BY-SA 4.0
2020-05-07T18:39:57.127Z
Useful information is a pure public good.
beroal
CC BY-SA 4.0
2020-04-27T01:03:50.283Z
2020-04-27T01:03:50.283Z
1muflon1
<p>I get why, say, the military is a public good, but I don't get why public roads are public goods, since they can't be non-rivalrous, given that at any time only a subset of the population can actually be on them.</p>

CC BY-SA 4.0
2020-04-27T09:46:45.227Z
This question and answer may be helpful: https://economics.stackexchange.com/questions/12520/why-is-a-fire-service-considered-to-be-a-non-rival-service-while-a-highway-is-c
Adam Bailey
CC BY-SA 4.0
2020-04-29T08:25:07.483Z
Who claims that roads are public and not just common goods?
I'm with Monica
CC BY-SA 4.0
2020-04-30T02:31:23.797Z
@I'mwithMonica No one claim that. The claim is "all public roads are public goods". It's not equivalent to "all roads are public and all roads are public goods".
Atonal
CC BY-SA 4.0
2020-04-30T07:30:38.773Z
@Atonal, sorry if my question was ambiguous. What I meant was: Where does your claim, that "all public roads are public goods" come from? I have never heard that claim before. "Public" roads are common goods. ("Public" in this context is not an economical term!) - Thus, the premise of your question seems to be flawed: They are not, period.
I'm with Monica
CC BY-SA 4.0
2020-04-30T10:34:40.220Z
@I'mwithMonica Ah, that makes sense! I first understood that to be the case here (https://mason.gmu.edu/~atabarro/PrivateProvision.pdf). Mind you that I don't have an Econ background, and I did not document my cursory review of internet resources! But now following, your questions, this "Samuelson and Nordhaus 1985: 48-49" seems to be an example (Found here: https://marketurbanism.com/2011/02/22/urbanism-legend-public-good/)
Atonal
<microeconomics><public-goods>
If public roads are public goods, in what way are they non-rivalrous?
Atonal
# If public roads are public goods, in what way are they non-rivalrous?

(Asked by: username_0 on 2020-04-26)

I get why, say, the military is a public good, but I don't get why public roads are public goods, since they can't be non-rivalrous, given that at any time only a subset of the population can actually be on them.

**Tags:** microeconomics, public-goods

> **Comments:**
> **username_1**: This question and answer may be helpful: https://economics.stackexchange.com/questions/12520/why-is-a-fire-service-considered-to-be-a-non-rival-service-while-a-highway-is-c  
> **username_2**: Who claims that roads are public and not just common goods?  
> **username_0**: @I'mwithMonica No one claim that. The claim is "all public roads are public goods". It's not equivalent to "all roads are public and all roads are public goods".  
> **username_2**: @username_0, sorry if my question was ambiguous. What I meant was: Where does your claim, that "all public roads are public goods" come from? I have never heard that claim before. "Public" roads are common goods. ("Public" in this context is not an economical term!) - Thus, the premise of your question seems to be flawed: They are not, period.  
> **username_0**: @I'mwithMonica Ah, that makes sense! I first understood that to be the case here (https://mason.gmu.edu/~atabarro/PrivateProvision.pdf). Mind you that I don't have an Econ background, and I did not document my cursory review of internet resources! But now following, your questions, this "Samuelson and Nordhaus 1985: 48-49" seems to be an example (Found here: https://marketurbanism.com/2011/02/22/urbanism-legend-public-good/)  

---

## 1 answers

### Answer by username_3 on 2020-04-27. Score: 7

It depends actually a non-congested road can be considered non-rivalrous as when you drive there you don’t really reduce the enjoyment or marginal utility of other people driving them.

However, once the road is congested it becomes rivalrous.

Also note that even though many textbooks include public roads as public goods this is actually not technically correct. Technically since roads can be protected by toll booths they are excludable so it’s not correct to categorize them as public goods, they are actually a separate category of quasi-public goods - that is goods that have many characteristics of public goods but also some characteristics of private goods.

However, it’s very hard to find proper example of pure public goods (although army is a good example, non-polluted air another), so often undergraduate textbooks that are less nuanced than graduate textbooks include quasi-public goods that are very close to public good in same category.

> **Comments:**
> **username_0**: Makes sense. However on non-polluted air being a pure public good, couldn't you say the more people there are, the less oxygen would be available for everyone else?! Specifically, given average O2 consumption of a human, there exist some number of humans where the global rate of oxygen consumption would be more than the rate of its production?  
> **username_3**: @username_0 yes it’s always all about context there is no worry that we ever run out of O2 at any realistic human population growth. Of course O2 at the international space station is neither non-rivalrous nor non-excludable. Same under water. However, on earth at and above sea level it’s one of the best example of pure public goods.  
> **username_4**: @username_3 I don't think your examples of pure public goods really hold. Because everything is quasi-public. You can totally have an army that only serves/protects one person/one group of people. That would be similar to the toll booth. Same goes with the non-polluted air. Air pollution makes the non-polluted air rivalrous (if I pollute air, it is not non-polluted for you any more) and then having e.g. fine-dust filters in your buildings gives you non-public clean air.  
> **username_4**: If you think the last statement is exaggerated, have a look at how things are handled in heavily polluted cities around the world.  
> **username_5**: Useful information is a pure public good.  

---

