TECHNOLOGY:Laser Axle Counter

So several firms are working on ways to count axles with suspended equipment well up off the pavement. One of the first with its product on the market is Schwartz Electro-Optics (SEO) of Orlando FL. It has just completed pre-sale testing of Autosense IIA, a scanning laser radar which counts axles, marks vehicle ends for counting, as well as makes a side profile which can assist classification. SEO has been supplying for several years Autosense II, a vehicle detection and classification systems that is mounted on a gantry and points down. It has about 700 of these in 17 different countries. Toronto’s 407-ETR is the largest installation, but the NY State Thruway, Florida’s Turnpike, Denver E-470 and Autostrada of Italy are other important customers. They are used in small numbers to count and classify vehicles for traffic management centers. In Florence’s historic city center they track mopeds.

The Autosense IIA has many parts in common with the II except that it uses a smaller and finer laser spot and different algorithms. It is mounted to scan sideways rather than downward. It can detect and count the points where the rubber meets the pavement to measure axles, as well as producing images of the vehicles from which the side profile is read. With the laser beam of the Autosense II it was found the system confused low slung diesel fuel tanks for tires, but the new sharper beam has fixed that problem. Those central lift axles on dump trucks – raised when running empty – can be a problem also.

Norman J. Abramson at SEO told us that the company recently did tests of 5000 vehicles on FL-441 northwest of Orlando in which it simultaneously took TV tape and put the new sidemounted Autosense IIA through trials. It got 99.7% accuracy on actual axle counts and a 0.6% false positive read (seeing an axle where none exists.)

The equipment sells between $8k and $5k apiece depending on the volume bought, and Abramson says that it should be slightly cheaper to buy than the combination of light curtain, loops and treadles, which he says it can replace. It can be programmed to signal or measure (1) vehicle detected as a signal for other equipment such as enforcement cameras or tracking antennas (2) vehicle speed (3) height of highest point of vehicle (4) end of the vehicle (5) number of wheels on pavement [axles] (6) tow bar detected (7) distance between axles (8) side area of the vehicle

SEO’s biggest selling line will be that the sidemounted laser is lower in maintenance and replacement cost, and greater in accuracy, than the loops, light curtails and treadles. It is a single piece of equipment that can be mounted in the roof canopy of the toll plaza, on a side pole, mast-arm or overhead gantry, well above the splash and dust of wheels. Normally it will shoot down about 45 to 65 degrees from the horizontal, perpendicular to the movement of traffic from above the adjacent toll lane. It could be of special advantage in highway speed tolling since unlike loops and treadles it is unaffected by speed. Treadles fall off in accuracy at high speeds due to vehicle bounce.

Some light curtains are being tried that can count axles by extending their ‘curtain’ beam right down to near the surface of the pavement where it shoots under the body of the vehicle and is broken by the tires to read axle numbers. Like all light curtains they need very frequent cleaning from dust, spray, mud and can be damaged by passing vehicles or aggressive motorists. SEO envisages the sidemounted IIA as an alternative to the overhead II where axle numbers and spacing data is needed, but hopes to continue to sell the overhead units.

Omron, a Japanese laser specialist is understood to working on a somewhat similar overhead based sensor to the SEO Autosense IIA product. Peek offers ‘smart loops.’ RF radars and machine vision equipment may also be adapted to add axle counting if there is a demand. (Contact 407 298 1802x137 www.seo.com)