LACBC Bike Count: Metro Bike Carrier Data

LACBC Bike Count iconBetter Bike had the pleasure of volunteering for the LACBC Bike Count this past Tuesday. From 7-9 AM and 4-6 PM we studiously counted pedestrians and cyclists at Wilshire & Santa Monica boulevards, one of the most dysfunctional intersections in the Los Angeles area. These are two of the busiest crosstown corridors and Beverly Hills can claim credit for doing nothing to make them safer for cyclists. 

Wilshire Santa Monica intersection aerialAt first glance, any cyclist would be crazy to bike across this tangle of traffic lanes, bus stops, and poorly-marked crosswalks. The Wilshire/Santa Monica intersection is old-school traffic management at its worst. Not a single 21st-century traffic management improvement finds a place here.

Because Wilshire is a deathtrap for cyclists and Santa Monica is a regional corridor with no use for bike lanes, we expect some cyclists to do the prudent thing and grab a Metro bus for the crosstown ride. We wondered how many cyclists choose to take their bike on the bus the Tuesday of our count, so we counted buses, carriers, and stowed bikes for both the AM and PM rush hours.

Bus Frequency & Carrier Use

We were particularly interested to know how frequent the buses actually ran and how many were equipped with the standard 2-up bike carriers. Turns out that bus service is very frequent on these two boulevards – 236 buses over the two two-hour rush periods – and Metro has outfitted 100% of their buses on these routes with bike carriers. That’s pretty impressive. But how often did cyclists made use of them?

Our back-of-the-envelope study put some numbers to carrier usage. An average of 28 bikes were carried per hour with (coincidentally) each two-hour period finding exactly 49 bikes transported. Though only approximate, the observed bike carrier usage gives some idea of the volume of multimodal commuting through Beverly Hills.

Bus use density map for the Westside
Figure 1: Bus use density

(Because Wilshire and Santa Monica are respectively ranked the #1 and #2 sub-regional corridors, this intersection is clearly the #1 transit junction on the Westside. Sunset Boulevard is a distant also-ran; the line there is ranked #6 and accounts for barely 20% of total boardings, according to Metro’s analysis for the subway extension. See Figure 1.

To gain a bit more insight, we counted buses, carriers and transported bikes by quarter-hour for the AM rush hour. (Figure 2.) First, cyclists’ use of carriers varied considerably by the quarter-hour, with a general trend toward heavier use in the 8-9 am hour. Caution to generalizers: observed variation is probably due to the ‘clustering’ phenomenon wherein rush hour buses tend to arrive¬†two or three at a time with longer periods between arrivals.

Metro buses and bikes per quarter-hour chart
Figure 2: Metro buses and bikes per quarter-hour, AM rush

Here’s where the chart is deceiving: it appears that the two plotted curves moving more or less in tandem visually suggests that carrier provision parallels demand for carriers. In reality, carrier provision varies somewhat according to the bus clustering thesis. Carrier use, however, did vary quite a bit more across the quarter-hours, from a low of 1 bike to 14 in that two-hour period.

Additionally, we can’t impute demand for carriers with any precision at all because the observed transported bikes only arrive when buses do – again in clustered fashion. In a better world with properly-spaced arrivals according to the Metro schedule, we would have a more precise reflection of cyclist use (a finer-grained picture) and something to really compare with the counts of cyclists moving through the intersection. (Stay tuned for that data!)

Carrier Use in the AM Rush

We can say that on average, Metro moved about 30 carrier slots though the intersection every fifteen minutes, slots that found on average six bikes. Still looking at quarter-hour figures, available capacity defined as some proportion of carrier slots available to a cyclists ranged from 96% available between 7:30 and 7:45 am to a low of 56% available slots between 8 and 8:15 am. Overall through the two-hour AM rush, on average, 80% of the bike slots were available.

On this particular Tuesday, carrier capacity in the AM rush far outstripped demand. With good reason: the cost to cyclists who want to transport a bike but can’t find an available carrier slot outweigh the fixed cost to outfit a bus. Those of us who have waited for an evening or weekend bus know how frustrating it can be to wait for an available carrier.

So, Metro has chosen to over-supply (100% of buses outfitted with carriers) to account for variation in demand and to cover clustering should traffic flow gum up the schedule. Or, maybe Metro just figured it was easier to outfit every bus on this route and avoid any criticism for not fully committing. (Maybe someone from Metro can enlighten us as to the prevalence of carriers system-wide.)

Capacity vs. Demand AM & PM Hourly

Metro  buses and bikes hourly, AM & PM rush periods chart
Figure 3: Metro buses and bikes hourly, AM & PM rush

As we said, we were surprised at the number of cyclists (98) who took a crosstown bus though this intersection during the morning and evening rush hours last Tuesday. But how many couldn’t find an available slot for their bike?

Well, we can’t say. But we can back up and look at the proportion of buses with no available space for a bike and relate that to the total number of buses passing through the intersection on these two busiest lines across both rush periods (Figure 3).

The AM columns (on the left) show the greater number of trips in the 8-9 am hour. (By contrast, the PM rush was more evenly balanced hour-to-hour.) And clearly demand for carriers was higher in that second hour, as 12 buses passed without space for a bike. Now, we saw no waiting cyclists turned away at the nearby bus stops, but if, on average, a bus on each route passes by every 10 minutes (12 buses total per hour) with fully-filled carriers, then probably somebody was left waiting for a carrier. We just have no way of knowing if cyclists were turned away.

That’s where excess capacity comes into play: between 8 an 9 am when buses were most plentiful, on average a bus would have traversed each route every two minutes, with about 30 per route per hour with an available carrier slot.

(Again, frequency is key; off the rush hour, there are fewer buses and so a filled carrier means a longer wait between buses. We’ve been there and would rather ‘ride it’ than ‘wait it’.)

Sometimes a Dual Carrier is not Enough

7 AM & 8 AM periods compared chart
Figure 4: 7 AM & 8 AM periods compared

Figure 3 suggests an anomaly in the data. Comparing the 7 am period to the 8 am period, the number of carried bikes increased from 26 to 31 – a 20% increase. Those same periods saw an increase in the number of buses from 51 to 70 – more than a 35% increase that outpaced the increase in carried bikes. Yet the number of observed buses with filled racks increased twelve fold (Figure 4).

Why? We’re open to suggestions. Maybe a cyclists-advocate-mathematician has an answer!