Its not just that the agency keeps determining construction based on political expediency (rather than ridership levels or trip reduction) but that the light-rail technologies it favors are wholly out-of-sync with Los Angeles' gargantuan urban form.
For instance, the trains on the Gold Line, which will soon offer service to Azusa through the Foothill Extension, currently have an average speed of only 21 miles per hour on its course from East Los Angeles to Pasadena. The entire journey takes about 54 minutes to complete (I frequently completed this route, back when I worked as I delivery driver, in as little than 25 minutes).
Part of the slowdown has to do with the numerous grade-level crossings the line must traverse. (something I could save a rant for at another time) But another is speed. The Ansaldobreda P2550 trains the agency uses have a top operating speed of 65 miles per hour, an upper speed limit typical for light rail (http://www.rtd-fastracks.com/main_398).
Although this may seem high, one has to remember that this is the maximum speed! On a free-flowing freeway, by contrast, cars routinely average 70 miles per hour (even when the posted speeds say 65 miles per hour) or higher.
Light-rail makes a lot of sense on short to medium-length routes through dense inner-city neighborhoods (e.g. Downtown or Boyle Heights) where it complements urban form and allows for frequent stops. And yet, on long routes to more outlying neighborhoods, distances which drivers would travel by freeway, a grade-separated technology that travels at faster speeds is needed.
What I'm thinking of, on routes such as the Gold Line Extension and the Sepulveda Pass line is a high-frequency form of commuter rail.
Commuter rail generally has a higher speed limit than light rail (ranging between 83 miles per hour and 125 miles per hour on the EMD F59PH locomotives that predominate on the Metrolink system). Almost all of the railway right-of-ways that are slated for light rail lines have operated as conventional railroad lines so conversion to commuter rail would be cheaper than light rail.
In addition to the construction of new commuter rail lines, the solution will require increasing the pitifully low frequencies on the extant Metrolink system (which currently only serves peripheral suburbs outside Los Angeles County) as well as adding both infill stations and outbound "reverse commute trains" (on the Orange County and Ventura County Lines).
In regards to commuter rail's interface with the light rail system, two options would be available.
One possible solution is to have light rail (and subway lines) serve the denser inner districts of Los Angeles County line (for instance, along the Wilshire Corridor and Gold Line to Pasadena) while having commuter rail take over for the outlying districts. For instance, one could ride the Gold Line up to the Lake Station in Pasadena but then connect to a commuter rail line (running from Burbank to San Bernadino) for the journey to Monrovia. In this sense, the transit system would mirror the historic division between the "Red Cars" and the "Yellow Cars" in Los Angeles' streetcar era.
A more exciting possibility would be the type of system found in the German city of Karlsruhe. The city's "Stadtbahn" seamlessly integrates tram lines in the city center with commuter lines to the suburbs, System cars are developed for compatibility with both tram and train tracks and electrification requiring only a quick change of wiring to transition between the two. It would be the equivalent (should an analagous "subway-train" vehicle be devised) of combining the purple line to Westwood with the Metrolink San Bernadino Line, so as to allow for a single journey from Miracle Mile to West Covina.
Is it a train? Is it a tram? No, its a tram-train!!
Given that such infrastructure would utilize existing infrastructure (both light rail or subway and rail), only minor improvements to bridge the gaps between the light-rail/subway and train tracks, besides the production of the vehicles themselves.
I don't know if a subway-rail interface is possible but the light rail-rail interface should be (given light-rail's similarity to a tramway).
Have the folks at Metro ever explored this possibility? Do they even know about Karlsruhe?