According to ehuacom, San Diego is a city in California, United States. The city has 1,382,000 inhabitants, with an agglomeration of 3,286,000 inhabitants (2021). In addition, the agglomeration is intertwined with the Mexican city of Tijuana, which has 1,642,000 inhabitants. In total, the urban area then has 5 million inhabitants, which in the north has grown attached to the immense metropolitan area of Los Angeles. These areas together have 23.5 million inhabitants.
According to MCAT-TEST-CENTERS.COM, the San Diego metropolitan area is quite vast. Unlike many other major conurbations in the United States, San Diego has relatively few suburbs. San Diego itself has 1,257,000 inhabitants, and the metropolitan area 2.9 million inhabitants. When the Mexican city of Tijuana is included, the agglomeration comes to about five million inhabitants. The largest suburb is Chula Vista, and the east side of San Diego is characterized by a number of smaller suburbs. North of San Diego are two larger cities; Oceanside and Escondido, but they aren’t as attached to San Diego as the other suburbs.
Unlike the metropolitan area of Los Angeles, San Diego is much more sparsely built, with 1,495 inhabitants per square kilometer, less than half that of Los Angeles. This is due to the fact that San Diego is dotted with canyons, gorges and cliffs, so much land is unsuitable for housing. These are more spread out, so there are relatively many city parks. The city of San Diego is therefore quite large, measuring 60 kilometers north-south. The conurbation extends for 85 kilometers from the Mexican border.
Also, the metropolitan areas of Los Angeles and San Diego are growing closer together, mainly around Escondido, which is closer to the outer suburbs of Los Angeles than downtown San Diego. San Diego is doing well economically, and crime is low. One downside is that house prices rose rapidly, more than tripling between 1998 and 2007. Many people have moved to the suburbs of the Inland Empire in Los Angeles, or even Mexico, and commute daily to San Diego. Population growth has stagnated from the late 2010s.
The Interstate 8 in San Diego.
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The San Diego Metropolitan Area Highway System
San Diego’s freeway network consists of four Interstate Highways and a number of State Routes that have been developed as freeways. The major highways for through traffic are the San Diego Freeway (I-5), Escondido Freeway (I-15), and Interstate 8. Interstate 805 forms an eastern bypass of San Diego, parallel to I-5. The State Routes that have been developed as freeways all have an interurban character, connecting suburbs with San Diego or suburbs with each other. State Route 52 is an east-west route through northern San Diego. Even further north in the city is State Route 56 an east-west route. State Route 54 forms an east-west axis through the southern suburbs. State Route 67 is a short highway in the suburbs of El Cajon and Santee east of San Diego. State Route 78 forms the northernmost east-west axis of the metropolitan area, connecting Oceanside to Escondido. State Route 94 forms the eastern approach road to downtown San Diego. Then State Route 125 forms a north-south axis through the eastern suburbs, which is of minor importance to through traffic. Finally, State Route 163 forms the northern approach road from downtown.
The highways in San Diego are quite wide, especially the north-south axes, as they handle the most traffic. In particular, the I-5 and I-15 have very wide stretches with 12 or more lanes. North of the intersection of I-5 and I-805 are 22 lanes, one of the widest stretches of highway in the United States. The State Routes are generally less wide, often with 2×2 or 2×3 lanes. Interstate 8 is also well developed, as it is the only east-west route connecting all other north-south highways.
Characteristic for the San Diego region are the many canyons, which means quite large differences in height in some places. These must be bridged with valley viaducts. As a result, I-8 is one of San Diego’s most spectacular highways, running through a canyon that all north-south highways cross via interchanges with high flyovers. The Cabrillo Freeway (SR-163) is one of California ‘s most scenic parkways. There is one toll freeway in San Diego, which is the southern portion of the South Bay Expressway (SR-125) through the suburb of Chula Vista.
The parkway design of the Cabrillo Freeway.
San Diego used to be such a big city. In 1940 the city had 200,000 inhabitants and San Diego County then had 289,000 inhabitants, which means that there was no real metropolitan area. San Diego’s first freeway began construction in 1942, the Cabrillo Freeway, later numbered State Route 163. The highway was completed in 1948 and was designed with parkway elements. Although it is considered a substandard, it is one of the most beautiful urban highways in California. 4 years later, in 1952, the first section of the San Diego Freeway, what became Interstate 5., opened would be, in the suburb of Chula Vista. In 1955 another short stretch opened in southern San Diego. However, the real construction of the I-5 mainly took place between 1962 and 1968. In 1973, the highway border crossing with Mexico opened, which is known as the busiest border crossing in the world.
In 1958, the first section of Interstate 8, which was largely completed in 1965 in the San Diego metropolitan area, opened only the westernmost section to traffic in 1969. Another older highway is State Route 94, the first section of which opened east of downtown in 1956. It was largely completed by 1963, only the easternmost segments opened to traffic in the early 1970s.
Further highway construction in San Diego started relatively late. This was partly because the growth of the city was not as large and fast as in the 50s and 60s around Los Angeles. In particular, the construction of the Escondido Freeway (I-15) started relatively late. Opened in 1970, this highway was largely completed in the region by 1985, except for a small portion south of I-8, which was not opened until 2000. Interstate 805 was also constructed as a bypass of San Diego between 1970 and 1975. This “bypass” is now located in the middle of the urban area, there is even more urban area outside I-805 than inside it, which is due to the rapid growth of the urban area from the 1970s. In the early 1970s, the first kilometers of the State Route 52 opened in northern San Diego, but it wasn’t until the 1980s and 1990s for significant portions to open. In 2011, the last link of this opened, also the most recent freeway opening in San Diego.
In addition, there were a number of highways that were deliberately built later, because the growth of these areas only took place later. One of these was the construction of the South Bay Freeway, the SR-54 section of it, in the late 1990s. Also, the construction of SR-56 through the north of the city did not go smoothly. Planning for this highway already started in 1964, but it was not actually built until the 1990s. The last section of this highway opened in 2004. In 2007, San Diego ‘s first toll road, the South Bay Expressway (SR-125), opened. Less than four years later, it was already bankrupt because the expected traffic intensities were far from being achieved.
Also in San Diego there have been planned highways that were not built in the end, although there are not many. One of these was the eastward extension of SR-56 through the suburb of Poway. It was also planned to extend SR-67 north from Santee to Poway as the third north-south highway through the metropolitan area, still east of I-15. This one has not been constructed either and the chance that this will still happen is nil. Despite this, San Diego’s highway network functions quite well for a city of this size and geographic difficulty. It is certainly not traffic-free, but the traffic jams are not nearly as big as in Los Angeles or San Francisco.
The highway network of San Diego was built under the direction of the Dutchman Jacob Dekema (1915-2017), born in Java to Dutch parents. He was the leader of District 11 of Caltrans between 1955 and 1980, during which time 95% of the freeways in the San Diego area were built. He graduated from the University of Southern California in 1937. He then worked at Caltrans, but served in the Navy during World War II. He worked for Caltrans in various counties of California after the war. In 1955 he was put in charge of District 11, which at the time had 40 kilometers of freeway. During his leadership from 1955 to 1980, that grew to 820 kilometers. In 1982, I-805 was named after him, the Jacob Dekema Freeway. He passed away in April 2017 at the age of 101.   
There are daily traffic jams in San Diego, although compared to its big neighbor Los Angeles it is not that bad. Most traffic jams are in the north-south direction, with the exception of I-8. This is because the agglomeration is mainly north-south oriented. In addition to the center, there are also large work locations in the ports, various military installations, and a few large industrial estates. The city is relatively bicycle-friendly, although the sometimes large differences in height and long distances limit cycling for commuting to the neighborhoods around the center. Due to the hilly area, there are few streets that can offer an alternative to the highways. The majority of traffic therefore goes on the highways, which in turn is favorable for cyclists.