Underpasses Everywhere

Urban Crossroads #32



An underpass intersection in Amman. (Khalil Soub)

Amman has no shortage of intersections with no traffic lights, usually consisting of two levels of underpasses (referred to as “tunnels”) located beneath street-level traffic. These have been constructed in Amman at a regular rate since the late-1970s. A few years ago, there seemed to be so many of them being built at a given time that a running joke stated that the city's motto should be “an underpass for every resident.”

Whenever one of those intersections was created, it simply transferred the traffic congestion problems it resolved to the following intersection. In turn, this necessitated converting that subsequent intersection into one of underpasses (with the occasional overpass), and so on. In the final result, complete streets have had to be converted into ones with a series of underpasses along their intersections. Streets that used to accommodate local stop-and-go service traffic now also have had to function simultaneously as fast-moving expressways. Zahran and Medina streets are two clear examples of such a development.

The verdict on these intersections is a mixed one. On the one hand, as the quantity and density of vehicular traffic has increased in Amman, these intersections have eased the flow of traffic at numerous bottleneck locations. I admit that I usually prefer driving along roads with these underpasses since they have no traffic lights at which to stop.

On the other hand, these intersections have had a disruptive effect on Amman's urban fabric. They have imposed high-speed expressways with intersections consisting of three layers of traffic located on top of each other on what otherwise are relatively small-scale, low-speed streets. In the final result, the streets with which we have ended up are neither of the above.

In cities all over the world, a need has arisen since the advent of the automobile age for high-speed arteries that cut through the city to allow vehicular traffic to move with ease and at relatively high speeds. These arteries complement high-speed ring-roads that wrap around the city. The arteries would include at least one that runs through one axis of the city (north-south for example) and another that runs perpendicular to it (east-west). What is absolutely crucial is that such cross-city arteries are completely separated from local vehicular traffic. Local vehicular traffic travels at a relatively slow rate, and involves a great deal of stop-and-go movement of vehicles as they park or stop to load and unload passengers and goods. Express traffic on the other hand involves non-stop, high-speed movement. The two types of traffic are mutually exclusive, and any overlapping of them will have disastrous results as fast-moving vehicles have to share the road with slow-moving stop-and-go traffic. The results will range from chaotic traffic conditions to outright collisions.

The complete separation of high-speed express traffic from the rest of the city's road system means that any access to the buildings or spaces bordering high-speed expressways cannot be from the expressways, but from local service roads. Buffer zones, usually landscaped, also need to be inserted between these expressways and the urban fabric bordering them to soften the visual effects of the expansive strips of asphalt and to absorb and distance some of the noise resulting from traffic. In a number of cases, such expressways are depressed below the level of the city streets and therefore separated from the city not only physically, but also visually. Areas at ground level, located above and adjacent to these depressed areas, in a few instances have been developed as parks to be used for recreational purposes as vehicles zoom underneath (as in Riyadh). In other examples, the results have been less successful, as when those expressways have been elevated above the city streets (as in Cairo), which not only scars the city visually, but also results in increased air and noise pollution.

In Amman, we unfortunately have ended up with the worse of two worlds. No differentiation whatsoever exists between high-speed expressways and roads accommodating local traffic, the two are simply jumbled together. This is especially evident at the locations of underpasses, where vehicles often driving at high speeds through the underpass suddenly face slow, if not halted, traffic just outside it because of the vehicles parking along the street to access adjacent buildings. I have witnessed a few collisions resulting from these fast moving vehicles not being able to slow down or stop in time to avoid the slow or parked vehicles just outside the underpass.

In the meantime, a number of Amman's originally small roads now have to accommodate high-speed express traffic, which is a near impossibility. It is understandable that the relative compactness of Amman, especially in its older areas, has not allowed for acquiring the space that urban expressways require to separate and buffer them from the surrounding urban fabric. Also, achieving complete separation through solutions such as depressing those expressways is a very expensive undertaking that is beyond the financial capacity of a city with relatively limited resources such as Amman. However, a number of areas through which those expressways run have been developed only recently, and any future-looking planning should have made arrangements for acquiring adjacent land to use as buffer zones through exercising the right of eminent domain, but this unfortunately has not happened.

It should be added that such underpasses do not relieve traffic congestion problems in the long run. This has been the experience all over the world. Although they may reduce traffic congestion in the short term, such intersections attract additional traffic since many drivers (myself included) will take the roads incorporating them even though they might have avoided those roads before the underpasses were constructed. In the long term, more traffic is attracted to these expressways, and as the number of vehicles passing through them increases, traffic congestion problems eventually will become even more exasperated.

Another problem relating to these intersections that seems unique to Amman is that although going straight through these intersections may be a relatively easy task at most times, making a left turn along them (and at many of them, most of the traffic is left-turn traffic) is an experience that only can be described as nightmarish. I would welcome traffic lights over the existing left-turn solutions any time. Ideally, left-turn traffic may be accommodated smoothly through cloverleaf intersections, but these require considerable space, which (as mentioned above) is not available along most expressways and intersections cutting through the city.

A foreign urban planner visiting Amman once remarked that the city's existing street layout and urban fabric will not be able to accommodate any increased traffic. Such a comment becomes painfully evident during the summer months, when car-driving expatriates and tourists flock to the city from the countries of the Gulf region, making Amman a very difficult city in which to drive. The solution is not in attempting to accommodate Amman's ever-increasing traffic, but in totally different approaches that range from developing an efficient public transportation system to even pursuing policies of decentralisation that would direct population increases (and the vehicles that come with them) to Jordanian cities other than Amman.

Mohammad al-Asad

January 27, 2005


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