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ModelCanon PowerShot A590 IS
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Focal Length5.8 mm; equivalent: 29 mm
Aperture ValueF3.2
White BalanceAuto white balance
FlashFlash did not fire, auto
Metering ModeMulti-segment
Shutter Speed Value1/1244 sec
ISO Speed Ratings80
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Exposure Time1/1250 sec
Exposure ModeAuto exposure
Max Aperture ValueF2.6
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Exif Image Width450 pixels
Exif Image Height570 pixels
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CompressionJPEG (old-style)
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Reflector in slot
The Massachusetts Highway Department performed extensive repaving work in June, 2009 at the rotary on Route 20 over Route 128/95 in Waltham, Massachusetts. But, after laying down smooth, new pavement, the Highway Department almost immediately ground it up to install sunken, reflectorized markers, as shown in the photo below.

This type of marker is appropriate on a high-speed limited-access highway where

  • the marker must be visible at a very great distance,
  • traffic at that distance is in line with the slot, rendering the marker visible,
  • Motor vehicles do not regularly travel over the reflectors, subjecting them to wear,
  • bicycles do not travel over the markers, risking crashes, and
  • snow plows would tear up protruding markers.

The Highway Department has an unfortunate history of using hardware only appropriate for limited-access highways on non-limited-access parts of projects involving those highways -- interchanges, overpasses, nearby roadways. In the past, the usual problem has been with parallel-bar storm grates that are hazardous for bicyclists. That problem appears to have been rectified in this project, to be replaced by a new one: sunken markers in slots used at the edge of the road. This one is on Weston Street (Route 20) east of the route 128 rotary. The Manual on Uniform Traffic-Control Devices, section 3B.13 discourages the use of markers on right edge lines except through freeway interchanges -- that is, the markers are meant to be used only on the freeway itself.

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Images and captions by John S. Allen unless otherwise indicated.