EDSA. Here's an analogy to describe its current (pre-2017/2018) role in the Manila highway network.
Imagine say a large enough city, like San Francisco. Imagine if the Freeway Revolt had been more extensive, and there was no Bayshore Freeway or Southern Freeway whatsoever, with 280 ending at 19th Avenue and the Bayshore Freeway ending in Brisbane or whatever. And in this imaginary scenario, only 19th Avenue provided the access to either bridge.
So that's kinda like EDSA but that doesn't really give you the scope of it. The city that the ring road runs through - Quezon City, the one-time Filipino capital from the 1940s to 1976 - actually has more people than Manila itself, with a population of 2.9 million - almost as much as Chicago! Manila on the other hand "only" has 1.7 million (twice as many people as San Francisco, and larger than San Diego as well)...in a 16-square-mile landmass. EDSA also skirts Makati, the most modern downtown in the entire country.
It's not hard to see why this has become the main street of the region, a role it had never been intended to take on. Older-generation interchanges, business driveways on every block, interregional traffic, and the usual stop-and-go patterns of the jeepneys along the route are compounded by multiple large malls (especially SM EDSA North in Quezon City, but also the massive Mall of Asia at the road's south terminus) as traffic generators.
DSC_5199 by
Chris Sampang, on Flickr
Overhead signage. "Ayala" is the exit to Makati's Ayala Center area, comprising of a popular local park and the Greenbelt and Glorietta mall complexes. Also note the advertising right on the median!
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Chris Sampang, on Flickr
H&M store from the SM Megamall in Mandaluyong. The overhead structures are for the MRT-3 mass transit rail line.
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Chris Sampang, on Flickr
Traffic on Christmas Eve morning.
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Chris Sampang, on Flickr
Advertising on a VMS.
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Chris Sampang, on Flickr
The intersection with North Avenue, where SM City EDSA North mall is located.
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Chris Sampang, on Flickr
Signage heading away from the North Luzon Expressway - note again the lack of road names on the overheads, only destinations.
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Chris Sampang, on Flickr
Westbound grade separation in Makati
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Chris Sampang, on Flickr
Offramp in Pasay which connects EDSA to the Ninoy Aquino International Airport
DSC_7420 by
Chris Sampang, on Flickr
Signage commemorating Japanese assistance on an interchange in Makati
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Chris Sampang, on Flickr
Offramp at the Magallanes Interchange which links EDSA and the South Luzon Expressway