The flaw in this analogy is that it assumes that a barrier must be both visual and physical. Semantics? Not really: visual and physical barriers are not necessarily the same thing. This distinction is very important to the high speed rail debate, and is totally lost in the Berlin Wall analogy, intentionally or not.
Strong Physical, Weak Visual
A barrier can be physically strong--preventing pedestrian, bike or auto access across the tracks, and negating the ideals of a walkable, bikeable community. And yet, that same barrier can be visually weak. The Caltrain tracks through Palo Alto (street view at right) are an excellent example of a strong physical but weak visual barrier. In a span of four miles, there are just nine places where pedestrians may cross. There are even fewer crossings for cars. And yet, the tracks are visually unobtrusive and concealed by vegetation.
In many locations along the Caltrain corridor, an invisible "wall" already exists today, so deeply ingrained into daily circulation patterns that few ever notice it. That's no wonder: it's been there since before any of us were born.
Strong Visual, Weak Physical
Some new grade separations envisioned for high speed rail, depending on how they are built, may create new visual barriers. The strong visual impact of raising the tracks, with the addition of 30-40 feet of overhead electrification wiring, understandably has some neighbors worried.
However, physical access would be preserved and even improved because trains would no longer interrupt pedestrian, bike or road traffic flows, as they currently do about 100 times a day. Given that physical access would be maintained (and possibly improved) by HSR, the analogy to the Berlin Wall falls apart. While the Wall's primary function was to deny physical access, the function of a grade separation is to allow physical access across the tracks.
A local, real-world example of a strong visual but weak physical barrier is found in Belmont. The retained embankment is ugly and intrusive, as shown in the opening photo of this post, but it has several crossings through it--for example, as shown in the photo at right, taken from just a few feet away. The Belmont Caltrain station, at El Camino and Ralston, has a very pedestrian and bike-friendly design with direct access across the tracks.
Grade Separation Design Values
Access across the railroad tracks can be optimized for different users, and the best grade separation design really depends on whose needs are prioritized first: bicycles and pedestrians, cars and trucks, or the train. No design will be perfect for all three. Many communities that have grown and gradually saturated their historical main arteries are now making an effort to relieve auto traffic by improving access and circulation for bikes and pedestrians. What are the features of a grade separation that promotes a walkable and bikeable community?
- Minimal grade change. That's not just a matter of convenience; the ADA requires extensive ramps or elevators where significant grade changes occur. Elevators in particular create maintenance and sanitation problems. While such features are sometimes necessary, they are generally expensive (also profitable to build!) and are neither pleasant nor quick to navigate. It is best to avoid this problem altogether, by keeping pedestrian / bike / wheelchair access as close as possible to grade level.
- Direct and short. The design of the access paths to a crossing should avoid forcing bike / pedestrian traffic onto circuitous detours from their intended path. If the point is to get across the tracks, let people get across the tracks quickly. Long access paths remove freedom of movement and make the user feel constrained and unsafe because of how long it takes to get across.
- Open sight lines. Tunnels and ramps that twist and turn without providing a clear line of sight to the other side do not convey to their users a sense of safety and destination. No amount of lighting, fancy landscaping or architectural detail can compensate this problem.