Reader comment of the day

The reader comment of the day goes to Jon Barsanti, who took a look at the job and population density maps I posted yesterday and then wrote:

"What the maps skew is the difference between the job density and the population density. The two scales do not coincide. What would be better is a map that illustrates the migration pattern of workers throughout the region."

Barsanti has a very good point. The job density and population density maps do not match up very well. I posted them because I do think they show some basic patterns in Los Angeles County: employment density is highest downtown and on the Westside, while population density tends to be high in the south and east parts of the county.

I wish -- dearly, dearly wish -- I had a map showing where all the people are going each day, such as how many people were going from South L.A. to the Valley, from the Valley to downtown, etc. The average commuting times for each city are available from the Census Bureau, but we don't know exactly where everyone is going.

Of the maps I posted, I tend to think the employment density is the more important. If we know where the target is, perhaps it's possible to make the appropriate road and transit improvements to get people there.

--Steve Hymon

Comments

[rla]

The graphic you are looking for is in the Technical Document of the Draft 2008 Long Range Transportation Plan on Metro's website. See Figure 5.13A at
http://metro.net/projects_studies/images/2008_lrtp_techdoc.pdf

[BOB2]

The populatin density maps were definitely wrong. What scale was this done at? Where is Pico Union, Mid Wilshire and Hollywood? I've run and plotted these density factors myself and this is obviously wrong. Who's goofy analysis was this?

Fact:, weekday home to work trips are only 20% of daily trips. Chained home to work trips another 10-12% . So on weekdays less than a third of observed trips are work trips. Another interesting fact is that nearly half of these work trips are likely to occur outside of the am and pm peaks. The worst congestion period is Friday evening peak, and many Freeway volumes on Saturday are actually higher without peak period congestion than on weekdays. Congestion is not solely a function of job housing location, it is a complex iterative system affected by many variables, from road geometry, to volumes, to accidents, to unstable flow phenomena, leisure and shopping travel, and the availability of alternatives. Congestion is a non-linear function, speed/flow curves are actually parametric. Traffic speed/flow is a last straw on the camel's back phenomena for those with less math.

This extremely simplistic explanation, that congestion is somehow only a function of jobs and housing is based upon clearly poor and possibly inaccurate data,. This is only a small part of the explanation of the causes of traffic congestion, and only during weekday peaks. As HL Mencken once observed: to every complex problem, there is always and simple solution, and it is invariably wrong?

[Daniel - The California Highway Guy]

You know, you might be able to get that information from MTA. They collect information on commuters for vanpool and carpool matching. Thus, they know where the employers are, and from there, the demographic information of their workers.