Who decides who gets to have kids?

[Quillz]

Some 3di's have become a real head-scratcher, such as one in Savannah: Why I-516 when 116 and 316 could've been used?

Nevada using I-580 makes sense because it fits into their state route numbering scheme, where 5xx is generally used for more local routes. It runs between Carson City and Reno, so it kind of fits the idea of it being localized. Even though from a geographic standpoint, I always thought I-180 would have made more sense.

I don't know about Georgia, but maybe they have a similar numbering logic?

[Scott5114]

Nevada using I-580 makes sense because it fits into their state route numbering scheme, where 5xx is generally used for more local routes. It runs between Carson City and Reno, so it kind of fits the idea of it being localized. Even though from a geographic standpoint, I always thought I-180 would have made more sense.

The downside of using 580 is that it was specifically a Clark County urban route number.

But 515 is a Carson City urban route number, so.........

[SSOWorld]

Most of the time, it's the women who decide.

Correct -- she is the gatekeeper.

Was I-238 born on Christmas?

One would wonder why I-794 and I-894 were used in Milwaukee.  State routes normally are always starting with 1 for 3-digit. Lately that's been broken.

[ilpt4u]

IL 194 existed in Illinois between the Kennedy/Edens Junction and ORD Airport before 90 was rerouted onto the Kennedy to the airport.

Sure, not an interstate, but was a freeway not very far from Milwaukee. Probably was best to not duplicate the number for a separate Milwaukee freeway

[TheStranger]

I've mentioned it before, but California's 3di assignment has generally been consecutive order, with some geography involved.

I-80 for instance:
280 and 480 were the loops that originated within SF (with 280 being originally planned as the westernmost route in town until the Junipero Serra extension north of Font/Brotherhood was canceled), 680 the outer belt from San Jose to Vallejo originally, then 880 as the Sacramento bypass with ends at both parents.  Current 880 is a 1980s renumbering.
180 skipped due to 1934-present CA 180. 
580 derives its number from the past I-5W designation.  380 in the early 1970s was thus the first new-build spur route, then the renumbering of 680 into Vallejo as 780, then 980 in the late 1970s.
Since I-80 is the only 2di in the Bay Area after I-5W was removed in the 1960s, pretty much most of I-80's child routes were in that region.


I-5:
205/405/605/805 were originally a geographic sequence from north to south, with 205 only being created in the wake of the move of I-5 from the 99 corridor (where I-5W would have followed today's 132 expressway west to today's I-580) to the current West Side Freeway route
The 1960s 105 (along the Slot portion of US 101/Santa Ana Freeway) was the only original spur; I-505 gets its number from its past planned designation as I-5W.  Current I-105 was a 1968 designation of what had been planned as a Route 42 freeway realignment.

I-10:
The original I-110 of the 1960s along the I-10/US 101 connector spur (San Bernardino Freeway) was the only proposed spur of the route in the original numberings.  Current I-110 and I-710 derive their numbers from the past state routes on those respective freeways (1934-1981 Route 11, 1964-1984 Route 7)

I-210 is the only loop route for I-10 in California and part of early interstate proposals.