"Don Kirkman" wrote in message
news:l98an159tp9bgmhiq071mvr0rqeiuhll4a@4ax.com...
> It seems to me I heard somewhere that IClast@JPS.Net wrote in article
> <1131714751.803553.56270@o13g2000cwo.googlegroups.com>:
>
>>The blue/red ones are part of the InterState Highway system. The
>>two-digit numbers are the primary highway numbers. The three-digit
>>numbers have meanings that I can't explain but I can tell you that
>>InterState Highway 80 is connected to InterState highway 380 connects
>>to
>>280, and there's 680 somewhere around Oakland, and perhaps others in
>>and
>>near San Francisco.
>
> That's pretty much it; the three-digit signs are alternate routes to the
> two-digit highway with the same number. In IClast's examples, 280, 380,
> and 680 are all (usually short or local) alternates for sections of 80.
> They generally serve areas off the main route like hotel/motel or
> tourist areas. If you follow them you eventually end up back on the
> primary I-route.
hmmmm....the recommendation here is to get out a good map. In other parts
of the country, 'alternate' usually denotes another routing that more or
less parallels the main one. Alternate US89 (US89A) through Arizona/Utah is
a good example. Sometimes this alternate routing takes you through a town
while the main one bypasses the town; both meet again on the other side of
the town. Business Loop I70 through Green River, Utah, is a good example.
This is not the case with the Ix80 designations in the SF Bay Area. For
example, I380 does not at all meet I80 - one end terminates at I280; the
other, at US 101. I580 runs from the east end SF/Oakland Bay Bridge part of
I80 southeast, then east, then southeast to connect with I5 southwest of
Tracy. I680 runs south from the Cordillia Junction area of I80 past I580 at
Dublin/Pleasanton to meet the junction of US101 and I280 in the south San
Jose area. I980 is a short segment joining I580 and I880 in the Oakland
area. I880 runs from San Rafael across the Richmond/San Rafael bridge to
merge with I80, then at the east side of the SF/Oakland Bay Bridge leaves
I80 to remain on the east side of bay, crosses US101 in San Jose, and
terminates at the intersection with I280 (where it continues to Santa Cruz
as hwy 17). I280, on the other hand, begins several blocks south of I80 in
the south of Market area of San Francisco, crosses US101, swings west and
then heads south to the junction of I680 and US101 in the south San Jose
area.
So if you are driving west on I80 from the Sacramento area, you'll encounter
junctions only with I580, I680, and I880. And while I80 terminates within
San Francisco at the junction with US101, none of these other three comes
anywhere close to San Franciso. If you take any of the three as an
alternate route to San Francisco, you'll have to take other
freeways/highways to get to San Francisco. In no case will you - without
backtracking - ever get back to I80 without leaving any of the three that
you've taken. And while you are on I80, you will never come across a
junction with any of the others - I280, I380, and I980.
As indicated earlier, check the map.
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