Testing the gap distance between Kassel Kerbs and Public Service Vehicle boarding steps

Abstract. This work examines the applicability of Kassel Kerbs (Profilbeton GmbH, Friedensstraße 1, D - 34590 Wabern and UK agents, Lafarge Redland Precast, Six Hills, Melton Mowbray, LE 143 PD Leicestershire) to be able to attain a 50-75mm boarding gap for Public Service Vehicles (PSVs) as required by Transport for London (TfL) for proposed 'Intermediate Mode' routes. Tests using a simulated PSV loading step and installed 180mm Kassel Kerbing were used to prove that the requirement is entirely attainable.

Method. To simulate a PSV loading step, a batten of wood was securely attached to the loading area of the interior of a Ford Transit van (figure1). The loading door was locked open. The batten was aligned horizontally with the outer face of the front and rear wheel hub covers. The batten bottom edge was 290mm from the road surface. This set-up was not adjusted during the test period.

Test. Using the Kassel kerb installation at the junction of the Upper Ham Road and Ham Common, towards Richmond-upon-Thames, the tests were carried out between 12.45 and 13.45 on Sunday, 25th March 2001. The conditions were dry at approximately 10 degrees ambient temperature. Runs were made repeatedly and measured after each attempt. Runs 1-3 were by a PSV driver with previous experience of using Kassel Kerb stopping. Runs 4 & 5 were by a driver having no previous experience of Kassel Kerb use, but attempting to draw in as close as possible. Runs 6 & 7 were done at above standard speed, and thus, through instinctivness, not using the self-guiding qualities of the kerb. Runs 8,9,11 &12 attempted to simulate standard service conditions. Run 10 was to achieve tightest possible alignment.

Kassel Kerb/PSV boarding step distance test

run	distance	driver	remarks	photograph
1	49	dw
2	41.5	dw
3	41	dw
4	33.5	ab	alternate driver
5	29	ab	alternate driver	fig.2
6	116	dw	at speed
7	83	dw	at speed
8	70	dw		fig.3
9	49	dw		fig.4
10	32.5	dw	to achieve tightness
11	62	dw	as a normal run
12	50.25	dw	as a normal run
average	54.73

Remarks. No difficulty was experienced achieving the required gap, except at additional speed. The self-guiding quality of the kerb design was readily experienced by both drivers, and whilst not as repeatedly accurate as rail guidance, was regarded as easily attainable. Achieving a 40-50mm gap was considered to demand extra drive concentration. Achieving 50-75mm gap was considered repeatable in daily PSV service conditions. The absolute minimum gap of 29-31mm was achieved only by the driver demonstrating determined overcoming of the inertia and gravity effects of the kerb design. Only in these extreme, but not unobtainable conditions, would tyre wear occur.

Random interviews with drivers on the 65 service (Armchair Travel) suggested little knowledge of the purpose of the kerbs or concern about protruding wheel nuts coming into contact with the kerbs. (This was not possible with 180mm high Kassel Kerbs, as installed). It is further understood that operators have concerns about additional costs being incurred by repeated close contact with the kerbs, due to additional tyre wear. Close monitoring of tyre wear, after driver instruction and training in the proper use of Kassel Kerbs, would provide an indication of the likelihood of tyre wear. It is, however, the opinion of the drivers of this test, that proper use of Kassel Kerbs to consistently achieve a 50-75mm loading gap, would not result in undue tyre wear. Tyre changing, at regular intervals, is further likely to nullify any tyre wear effects.

Summary. Without special skills but with due care, it is possible to repeatedly attain a distance between a Kassel Kerb outer top edge and a PSV loading step outer top edge, of between 50 to 75mm. (This compares with the 80mm gap between the platform and boarding step of Bombardier railcars used on the Croydon 'Tramlink'.) The repeated use of Kassel Kerbs as outlined above, is unlikely to produce additional tyre wear. With proper design of vehicles and driver training, this practice would provide customers with a better quality of service.

Ashley Bruce MaRCA. DipAD
David Wilsher