Travel-Time Impacts of Mayor
Midtown-Manhattan Crosswalk Barriers
8 January 1998
The Barriers Cost Pedestrians 8-10 Times as Much Time as They Save Motorists
Barring pedestrians from half of the crosswalks on five avenues (6th, 5th, Madison, Park and Lexington) lengthens crosstown pedestrian travel times across the affected area (from 6th Avenue to Lexington) by more than a minute and a half (101 seconds, or 16%).
In comparison, even granting Mayor Giuliani’s (unsupported) claim of a 20% improvement in vehicle travel times, the same trip in a motor vehicle is shortened by only about a minute (64 seconds) in a crosstown vehicular trip covering the affected area.
Thus, the typical pedestrian loses 1 1/2 times as much time as the typical motorist gains.
Moreover, crosstown pedestrian traffic vastly outnumbers vehicular traffic — by around 6 or 7 to 1. Thus, the aggregate lengthening of pedestrian travel times exceeds the shortening of vehicular travel times by around 10 to 1. Even if the barriers improved crosstown vehicular speeds by 30%, the total time costs to pedestrians would still outweigh the time savings for motorists by almost 8 to 1.
And whereas the increases in pedestrian travel times reflect physically-lengthened journeys (and associated street-crossing waiting times) and thus would be permanent, the improvements in vehicular travel times are likely to prove transitory as new vehicle trips by opportunistic drivers "use up" the reduction in vehicular congestion. Finally, the barriers force pedestrians to make new street crossings through streams of turning traffic, for a considerable increase in risk for them.
The bottom line on the barriers: pedestrians lose 8-10 times as much
time as motorists gain, and are exposed to greater danger; and the pedestrian
losses are permanent while the motorist gains are probably transitory.
On Dec. 23, 1997, the New York City Police Department initiated a pilot program intended to improve crosstown motor vehicle speeds in midtown, which are notoriously slow. Possible effects on pedestrians, as the Police Department acknowledges, were not considered. At five avenues crossing 49th and 50th Streets from 6th Avenue to Lexington Avenue, 3-foot high barriers and an intensive police presence bar pedestrians from avenue crosswalks so that these can be used exclusively by turning vehicles.
For example, to cross 5th Avenue, a southbound traffic artery, pedestrians must use the crosswalk on the north side of the street. To cross northbound Madison or 6th Avenues, pedestrians must use the south crosswalk. Thus, half of crosstown pedestrian trips that previously involved crossing only avenues now require zigzagging across two additional streets.
The pilot program was originally designed to run until approximately Jan. 5, but Mayor Giuliani has extended it until Jan. 12 or 15.
The program has been wildly unpopular with pedestrians and has been roundly ridiculed in the press. The mayor has staunchly defended it while attacking critics as "anti-car." On Dec. 30, the mayor said the program has improved traffic flow 20-30% and will potentially save lives by permitting emergency vehicles to travel faster.
This paper is intended to remedy the Police Department's failure to consider the effect on pedestrian travel times.
A Typical Crosstown Pedestrian Trip: Before
Consider a pedestrian trip along 50th Street from the west side of 6th Avenue to the east side of Lexington Avenue — a distance of 2355 feet. (The particular trip length or configuration is unimportant; the typical trip chosen here is used to derive pedestrian and vehicular before-and-after travel time ratios, which will vary little if at all for other crosstown trips.) At an assumed walking pace of 3 mph (4.4 feet/second), the time actually spent walking is 535 seconds.
However, five avenues must be crossed, involving possible waiting time. A typical traffic-signal cycle lasts approximately 85 seconds, of which 52 seconds is green/walk for north-south travel and 33 seconds is green/walk for east-west travel. We estimate that pedestrians typically wait an average of 21 seconds to cross an avenue (see Appendix). This adds 105 seconds (5 x 21) to the journey, for a total of 640 seconds (535 + 105), or 10 minutes and 40 seconds.
The "effective" speed for the pedestrian is 2.51 mph (calculated by dividing 2355 feet by 640 seconds, and converting from feet per second to miles per hour by simultaneously dividing by 5280 and multiplying by 3600).
A Typical Crosstown Pedestrian Trip: After
Now consider the same trip with the pedestrian having to detour to the non-barriered avenue crosswalks. Its duration is increased in two ways: greater distances reflecting the detours across the side streets; and new waiting times incurred in crossing those streets.
First, the pedestrian must make six street crossings. Assume the pedestrian’s journey would ordinarily proceed eastward along the north side of the street (i.e., from the northwest corner of 50th and 6th to the northeast corner of 50th and Lexington). The pedestrian must now cross:
• from the north to the south side of 50th Street, along the west side of 6th Avenue;
• from the south to the north side of 50th Street, along the west side of 5th Avenue;
• from the north to the south side of 50th Street, along the west side of Madison Ave.;
• from the south to the north side of 50th Street, along the west side of Park Avenue;
• from the north to the south side of 50th Street, along the Park Avenue median;
• from the south to the north side of 50th Street, along the west side of Lexington.
Each crossing is approximately 30 feet from curb to curb. Thus, the six crossings add 180 feet to the trip, converting a 2355-foot journey to a 2535-foot journey. At a walking pace of 3 mph, it takes 576 seconds to cover the distance, 41 more seconds than before.
Second, each street crossing involves possible waiting time. We estimate that pedestrians typically wait an average of 10 seconds to cross a street (as opposed to 21 seconds of average waiting time for avenue crossings; see Appendix). The six street crossings thus add 60 seconds (6 x 10) to the journey.
Total travel time is thus the sum of: 576 seconds walking time; 105 seconds waiting time to cross avenues (as before); and 60 seconds waiting time to cross streets. Total travel time is 741 seconds, or 12 minutes and 21 seconds.
Although the pedestrian has walked 2,535 feet, the true (or "net" or "intended") distance is the previous 2355 feet. Dividing this by 741 seconds (and converting from feet per second to miles per hour) gives the new travel speed of 2.17 mph. The speeds are incidental, however; what matters is travel time, which has increased by 101 seconds.
Summary of Results for Crosstown Pedestrian Travel
Old travel time for typical trip: 640 seconds
New travel time for typical trip: 741 seconds
Increase in travel duration: 101 seconds, or 16%
Vehicle Travel Times and A Comparison with Pedestrian Impacts
The mayor has claimed that his pedestrian barriers have improved crosstown vehicular speeds by 20-30%. Although no evidence has been provided to support this claim, we accept it arguendo and use it here for purposes of evaluation.
Midtown vehicle speeds were reported earlier this month as averaging 6.2 mph. However, crosstown speeds tend to be even slower. To estimate actual crosstown vehicle speeds on 49th and 50th Streets, we consulted the "Speed Books" maintained by traffic expert and engineer Sam Schwartz (the Daily News’ "Gridlock Sam"), which sample and record vehicle travel times and speeds at hourly intervals on each city block. Based on the most recent measurements, taken on 12 hourly intervals on four different days in 1995 and 1996, crosstown vehicle speeds on the two streets average 4.2 mph. A 20% improvement would produce a gain of 0.84 mph, to a speed of 5.04 mph. (These speeds reflect waiting time, including at intersections.)
The relevant parameter, of course, is time, not speed. At the old speed of 4.2 mph, a vehicle takes 382 seconds to cover the crosstown distance of 2355 feet (2355 divided by 4.2, times 3600 divided by 5280). At the putative 20%-improved new vehicular speed of 5.04 mph, the same trip in a motor vehicle takes 319 seconds, a saving of 64 seconds (rather than 63, which reflects rounding error).
In comparison, the same trip by a pedestrian has now been lengthened by 101 seconds. Moreover, crosstown-proceeding pedestrians far outnumber crosstown-proceeding vehicles. Official figures on relative traffic volumes are not readily available. However, on Jan. 6, 1998, personnel from Transportation Alternatives counted pedestrians and motor vehicles per hour entering 5th Avenue, eastbound, as follows:
From East 48th Street: 3732 pedestrians, 386 vehicles — a ratio of 9.7 to 1.
From East 50th Street: 3618 pedestrians, 352 vehicles — a ratio of 10.3 to 1.
Accordingly, we assume a 10-to-1 ratio of pedestrians to vehicles for crosstown travel.
Granting an average vehicle occupancy factor of 1.5, the ratio of crosstown pedestrians to crosstown motorists is 6.7 to 1.
Thus, for each vehicle occupant saving 64 seconds, 6.7 pedestrians are losing 101 seconds each, for an aggregate loss of 675 seconds — slightly over 10 times as much.
(Parallel calculations for an assumed 30% improvement in vehicular speeds yield a ratio of pedestrian losses to motorist gains of 8 to 1, calculated by substituting average motorist gains of 88 seconds for the 64 seconds used above.)
It is true that some vehicular traffic — freight and, especially, buses — has a high economic value. (The mayor’s claim that his experiment may save lives by expediting emergency vehicles is purely hypothetical and is unverifiable without empirical data on lives lost due to traffic delays.) But much pedestrian traffic has a high economic value as well — consider the shopper approaching Tiffany’s or the attorney walking to a meeting with a client or another attorney. Moreover, pedestrians are less well equipped than motorists to withstand delays. Not only do pedestrians lack shelter from cold, rain, etc., as well as the greater diversions and comforts available to motorists; the very essence of walking is its directness in proceeding from Point A to Point B — a quality uniquely abridged by the barriers.
Finally, police officials assert that the barriers improve pedestrian safety by separating walkers from turning cars. This claim plainly inverts reality since, as shown here, the barriers roughly double the number of intersection crossings pedestrians need to make. For every avenue crossing supposedly made safer by keeping turning cars separate (an option previously available, in any event to pedestrians, who could always choose the long way around if they felt safer that way), pedestrians must now perform a new street crossing with vehicles turning from avenues onto the side street.
The Police Department does not appear to have noticed that it could improve pedestrian safety at every NYC crosswalk by visibly and stringently enforcing the pedestrian’s legal right-of-way over turning vehicles. The advent of the new year would be a propitious time for the mayor to move boldly to reduce pedestrian endangerment by motor vehicles, perhaps beginning with release of the annual but long-delayed Traffic Fatalities in New York City reports for 1995 and 1996. An estimated 226 pedestrians were killed by motor vehicles in New York City in 1996; the public needs and deserves official statistics as a basis for remedial action.
Appendix: Estimating Pedestrian Waiting Times for Street and Avenue Crossings
Typical midtown traffic-signal cycles are 50-54 seconds of green (walk + flashing don’t walk) for north-south travel and 30-36 seconds of red (steady don’t walk). We assume 52 seconds of green for north-south and 33 seconds of green for east-west, with cycle totals of 85 seconds.
A pedestrian crossing an avenue and approaching the curb observes either a walk signal (including the flashing don’t walk) or a don’t walk signal. In 52 out of 85 crossings, the signal will be don’t walk. Average waiting time in this circumstance is 26 seconds (one-half of the don’t-walk duration of 52 seconds).
During the 33 out of 85 crossings in which the signal reads walk when the pedestrian approaches, the pedestrian will walk unless the walk signal is near the end of the cycle. We assume the pedestrian will walk so long as there are 8 or more seconds remaining in the cycle. Thus, in 25 out of 85 crossings there is no waiting time. In the remaining 8 out of 85 crossings, the pedestrian must wait an average of 4 seconds for the signal to turn to red (steady don’t walk), plus 52 seconds for the red cycle to conclude.
Arithmetically, typical waiting time for crossing avenues is thus the sum of:
• 52/85 (probability of red) x 26 seconds (average waiting time); plus
• 25/85 (probability of enough green to proceed) x 0 (no waiting time); plus
• 8/85 (probability of green but "too late to cross") x 56 (4 + 52) seconds waiting time.
The result is: 21 seconds average avenue-crossing waiting time.
Waiting times are less for street crossings, since north-south movement has more green (walk) than red (don’t walk). The calculation follows the same format:
• 33/85 (probability of red) x 16.5 seconds (average waiting time); plus
• 44/85 (probability of enough green to proceed) x 0 (no waiting time); plus
• 8/85 (probability of green but "too late to cross") x 37 (4 + 33) seconds waiting time.
The result is: 10 seconds average street-crossing waiting time.
Note that we have not considered the possibility that pedestrians may be able to reduce waiting times by choosing street and avenue crossings in accordance with traffic signals. This could attenuate somewhat the worsening of travel times calculated here. On the other hand, we have probably understated waiting times by assuming that the walk and don’t walk signals are randomly distributed. In fact, consecutive street and avenue crossings, of which there are five pairs for a crosstown walk across the affected area, are linked; one who has just crossed a street, taking an estimated 7 seconds to do so, then faces 26 seconds of waiting time before obtaining a walk signal to cross the avenue, rather than the 21 seconds we derived based on random signals.
At least as importantly, we have not considered that increased pedestrian congestion on crosswalks and sidewalks would reduce walking pace from the assumed 3 mph. Avenue crosswalks will be doubly congested since half have been taken out of service. And street crosswalks and sidewalks will also be more congested, since the same number of pedestrians are now having to cover greater distances for the same journeys.