Grades of Guideway

Right of way comes in three grades: 'Separated', 'Exclusive', 'Dedicated'.

Dedicated is the lowest grade. A lane nominally belongs to one mode, an obligation more commonly honored in the breach. Think of HOV lanes and bicycle lanes.


Exclusive can be though of as 'excluding'; exclusive use is maintained through barriers. Exclusive guideway is never continuous--there are always gaps in it, typically at intersections.

Separated is similar to exclusive, except that it is continuous. Typically, this requires grade separation, if only where the guideway intercepts other rights of way.


Heavy railways (commuter rail, freight rail) have separated guideway, for the simple reason that trains can't stop quickly. Where they must cross other roads 'time-separation' (railroad gates) are used. Where this generates unacceptable levels of delay for the cross-streets (a train can take minutes to pass) grade-separation is used. Typically, this requires an overpass for cars traveling over the road. In cases where there are too many roads, the railroad may be buried. The 'cut and cover' model of a trench with a roof were how the first subways were built. (Actual tunnels came later). In some cases (Alameda Corridor, in LA), digging an uncovered trench for the railway is simpler than many bridges.


Light railways have a mix of Separated, Exclusive, and Dedicated. Most light railways make use of some portion of old freight track, which are already time-separated. Some light rail systems provide Separated guideway by running down the center of freeways (Portland) or on elevated structures (Los Angeles, Salt Lake). Light rail on streets (a train in in tram-mode) typically has Exclusive guide way, with intermittent sections of Dedicated guide way. San Diego and Buffalo, two or the first cities to build light rail, made use of this. Light rail vehicles weigh less than heavy rail vehicles, and so can stop more rapidly. Streetcar/Tram vehicles weight even less, so they can stop faster and are even more suitable for on-street use.

The decision to use either Exclusive or Dedicated right of way is one of cost and safety. Without barrier separation, conflicts with turning cars results in accidents. Sadly, even Exclusive guide way is no guarantee against human stupidity.





Higher barriers, which prevent drivers from crossing them, may be safer. The trade-off is that first responders/emergency vehicles lose the ability to make left-turns and U-turns across the street, due to the curb. To accomodate this, curb heights vary between systems.





There is a fourth grade of right of way: Shared. This is what regular buses have. It offers no speed advantage to the transit vehicle over a regular automobile. Once the time consumed with exiting the flow of traffic, boarding and alighting passengers, and re-entering the flow of traffic is considered, transit vehicles in shared right of way travel at about half the speed of an automobile.


In contexts where right of way is scarce or political will lacking, Shared and Dedicated guide way are more common, to the detriment of transit vehicle speed, reliability and safety.  A streetcar operating in shared guide way has minimal advantage over a bus. (The minimal advantage  is that is cannot leave the flow of traffic, and so loses less time entering/leaving the traffic lane).



BRT systems are cheap to build, and largely unregulated. Consequently, they vary wildly. They make use of every kind of guide way.

Grade-Separated 




Time-Separated 
(LA Orange Line), for a time. Drivers ignored them, causing crashes. It still experiences issues with drivers running red lights. Grade-separation is in the works.

Exclusive - Fenced


Exclusive - Curb




Dedicated - Median



Dedicated - Side

Transit Phases

Urban Transit in the United States has six major phases**:

1. Street Railroads
2. Subways/Elevated
3. Street rail
4. Bus-titution
5. M/ART
6. Light Rail

Street Railroads is exactly as advertised: Railroads reaching the city center, run on city streets. Noisy and dangerous, they are largely extinct. Most cities relocated several of them to a common corridor (typically as part of a Union Station effort). Building a 'viaduct' over them was a popular addition after WW2. Never electrified, they belched smoke and scalding steam as they traveled

Subways/Elevated were the first round of solutions to street railroads. Two solutions emerged: elevating them, and under-grounding them. As elevating is cheaper than excavating, it was the preferred alternative. (And railroads already knew how to build viaducts). Manhattan once had elevated rail-lines running down second and 9th avenue (of which the High line is the remainder). London forced another solution. The 'City of London', the original Roman square mile inside the greater metropolis of London has its own municipal government. Disliking the nuisance effects of railways, they simply banned them on city streets. (And now you know why London has so many railroad stations). But the value of bringing a rail-line INTO the center of London was simply too great, and so the Under-grounding began, in 1863. Chicago, with it's plethora of railways, still maintains its elevated stations ('The El').

Street rail: Everyplace with even a presumption of being a 'city' built a street railway. Using railroad track, these were smaller, lighter vehicles called 'trolleys'. There were a handful of attempts to draw them using engines, but electrification (using the pantograph) became endemic.* 

Inter-Urbans: A hybrid streetcar/railroad deserves a passing mention, if only for it's later importance for light rail. Combining street-running sections in urban centers, and railroad right of way between cities, they filled a niche market, typically by connecting urban destinations to entertainment or educational institutions. Some used trolleys, and some were special 'school trains'. 

Bus-stitution represents the dark age of urban transit. (To those who love trains, at least). Worn out trolleys were replaced were shiny new buses. (Cue Roger Rabbit). Streetcars were already in decline beforehand. The only rail routes to survive were underground/elevated systems, or places with awkwardly narrow tunnels. 

M/ART refers to the period between WW2 & the advent of light rail in the United States.  But in 1970, we recognized we had 'an urban transportation problem', which is the preferred euphemism for the explosive growth in traffic congestion.
Transit was the clear solution. But even the solution was a problem. Private companies had built most of the transit infrastructure before 1928, and municipalities getting into the game only in response to their failure. But no private entity was willing to build transit in 1970--competition from the automobile was just too fierce. Conservative pundits love to argue that this reflects the innate attractiveness of the automobile. They also love to ignore the billions of dollars in Federal subsidy provided for the Interstate Highway system. So, it order to compete with the automobile, transit projects required a subsidy. Given that the 70's were sort of the high-water mark of 'big government' and centralized planning, it became a Federal project.


None of them did terribly well, at least at first. They had very high costs per rider. For some of the systems, for some years, it would have been better to either a) buy everyone a cheap car, or b) put all of the money into buses. They've done better over time, as traffic congestion has worsened, and developers have responded to the accessibility premium of locations near them, so more things are near them. BART won its spurs when the Bay Bridge collapsed. The DC metro has become the most-ridden transit system in the US.

Light Rail The return of the inter-urban! Known as 'City-Rail' (Stadtbahn) in Germany, it made use of freight right of way, with street running portions in the center of cities. APTA called them 'light rail' so suburbs would accept them. Successful, at least judging by their popularity.  They make use of a variety of types of running-way.

Streetcars are history repeating itself. They are street-rail come again--trolleys operating in mixed traffic.  Portland has made them famous, and their use as a successful economic development project means that every major city in America is either building one, or planning to. The dividing line between street cars and light rail is not a clean one. (Salt Lake has a 'streetcar' in its own railroad corridor, and a 'light rail' on a city street'.)
Both make use of all types of running way. Streetcars generally have shorter lines, smaller vehicles, lower speeds, and more frequent stops. My analysis showed that average stop spacing is most distinctive. Portland, Tucson and the Tacoma Central Link all have an average stop spacing about half that for other systems. 

*Yes, cable-cars existed. Yes, a number of hilly places used them, most notably San Francisco. But even more places used funiculars, and I'm not mentioning them. Today, they are both simply exotic survivals. 

**BRT will require discussion elsewhere

**CRT too. 

1970's Rail

There were five Federally funded heavy rail transit systems*** built in the 1970's: MARTA, BART, MetroRail, and the Washington DC METRO

In the history of rapid transit the United States, almost nothing was built between 1928 and the 1970s. (Cleveland's heavy rail the noted exception*). And for good reason--demand for transit collapsed.  But in 1970, we recognized we had 'an urban transportation problem', which is the preferred euphemism for the explosive growth in traffic congestion.

Transit was the clear solution. But even the solution was a problem. Private companies had built most of the transit infrastructure before 1928, and municipalities getting into the game only in response to their failure. But no private entity was willing to build transit in 1970--competition from the automobile was just too fierce. Conservative pundits love to argue that this reflects the innate attractiveness of the automobile. They also love to ignore the billions of dollars in Federal subsidy provided for the Interstate Highway system. So, it order to compete with the automobile, transit projects required a subsidy. Given that the 70's were sort of the high-water mark of 'big government' and centralized planning, it became a Federal project.

None of them did terribly well, at least at first. They had very high costs per rider.** They've done better over time, as traffic congestion has worsened, and developers have responded to the accessibility premium of locations near them, so more things are near them. BART won its spurs when the Bay Bridge collapsed. The DC metro has become the most-ridden transit system in the US.

Many of the characteristics of these systems would carry over into later light rail planning and systems.

________________________________________________________________________

*Planned 1920, partially built 1929-1930, finished 1955-1958.

**For some of the systems, for some years, it would have been better to either a) buy everyone a cheap car, or b) put all of the money into buses.

***DART, despite the similarity of names, is not actually part of the M/ART transit cycle, but part of the 1982+ light rail cycle, starting operation only in 1996. (Initial efforts to fund it began in 1983).

A Concise History of Rail Transit in America

Modern transit comes from two historic lineages: Steam railroads, and horse-cart street railways. To operate in an urban environment, steam railroads underwent a number of modifications. To reduce conflicts with street level traffic, were either elevated or under-grounded. At some point, they were also electrified, typically use a third-rail system. Once that occurred, expansion required the continued use of grade separated, exclusive guideway, so no one touched the third rail and died. In contrast, street railways were electrified as trolleys, using a pantograph. (Cable-cars can be thought of as a 'dead branch' alternative to electrification). The converging modes of electrified heavy rail and street railways were hybridized as the "Inter-urban". Electrified the whole-way, using a pantograph, and running in a mix of at-grade and tunnels. After the second World War, almost all pure street running 'trolley' systems were 'bus-tituted' out of existence, while some inter-urban systems survived. The survivors all had some off-street running-way, viz: RTA Streetcars, San Francisco cable car, MBTA Green Line & Ashmont–Mattapan High Speed Line, SEPTA Subway–Surface Lines: Suburban Trolley Lines & Girard Ave Trolley, RTA Rapid Transit: Blue and Green Lines, Newark Light Rail, Muni Metro. Between ~1930-1972 is sort of a 'Dark Age' for urban rail--almost nothing new is built. Then there is a resurgence of heavy-rail systems to deal with traffic congestion: BART (1972), Washington Metro (1976), MARTA (1979), Baltimore Subway (1983), and Miami-Dade (1984). All run at-grade in the suburbs, and in tunnels in the city center. About 1980, America adopts the Stadtbahn/'City Rail' concept from Germany, and APTA coins it 'Light Rail'. It runs at-grade in the suburbs, and at-grade in the city-center, like the inter-urbans. Being regulated as 'light' rail, it is allowed to operate in mixed-traffic with cars, making it easier/cheaper to build. Over time, the surviving inter-urbans are rebuilt/revitalized, making use of the same vehicles as the new 'Light Rail' systems. Circa 2001, Portland reinvents the 'streetcar', which runs at-grade, in mixed traffic, with smaller vehicles, and making extensive use of single-track.

Now, to get back to what is 'Rapid' transit: Rapid transit is something that has it's own (unshared) guideway. Subways, elevated rail, commuter rail all clearly meet this standard, as do most of the 'Metro' systems of the 1970's heavy-rail revival. But the surviving inter-urbans and new light rail systems are a confusing mix: They have portions of exclusive guideway, so they have rapid transit portions. But LRT means 'Light Rail Transit' rather than 'Light RAPID Transit'. This gets confusion in the context of BRT, which actually means 'Bus RAPID Transit'. BRT gets developed in Latin America as a sort of bus version of a heavy rail system--buses with unshared guideway. But that's another topic. In summary: HeavyRail = Rapid, Streetcar !=Rapid, LRT !=Rapid...but does have sections that could be. (Cable-cars get lumped in with LRT largely on the basis of Cable-car != heavy-rail.)

And finally: Metro!=Heavy-rail, but Metro ⊂ Heavy-rail. Freight, Metro, Subway, Elevated, Commuter Rail ⊂ Heavy-rail.

=     Equal to
!=    Not equal to
⊂    Is a subset of.