Here's a simple test case:

library(data.table)
library(circular)
X <- data.table(Time='2013-01-01 05:00:00', speed=5.0, direction = circular::circular(22))
Y <- data.table(Time='2013-01-0117:00:00', speed=4.5, direction = 172)
rbind(X,Y)

The manual page for data.table::rbindlist continues to say this:

 If column ‘i’ does not have the same type in each of the list
 items; e.g, the column is ‘integer’ in item 1 while others are
 ‘numeric’, they are coerced to the highest type.

But that is no longer the behavior I see. Could type coercion be done at least optionally?

`> sessionInfo()
R version 3.4.4 (2018-03-15)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: Ubuntu 18.04.2 LTS

Matrix products: default
BLAS: /usr/lib/x86_64-linux-gnu/openblas/libblas.so.3
LAPACK: /usr/lib/x86_64-linux-gnu/libopenblasp-r0.2.20.so

locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=en_US.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] graphics grDevices datasets utils stats methods base

other attached packages:
[1] REhedge_0.2.42 REdata_0.0.6 REveal_1.10 REviz_0.1
[5] circular_0.4-93 bindrcpp_0.2.2 data.table_1.12.2 maps_3.3.0
[9] odbc_1.1.6 devtools_1.13.6 testthat_2.1.1

loaded via a namespace (and not attached):
[1] readxl_1.2.0 backports_1.1.2 spam_2.1-4
[4] sm_2.2-5.6 plyr_1.8.4 lazyeval_0.2.1
[7] sp_1.3-1 rclipboard_0.1 crosstalk_1.0.0
[10] leaflet_2.0.2 ggplot2_3.1.0 digest_0.6.19
[13] htmltools_0.3.6 gdata_2.18.0 magrittr_1.5
[16] memoise_1.1.0 cluster_2.0.6 aws.signature_0.4.4
[19] openxlsx_4.1.0.1 Metrics_0.1.4 readr_1.3.1
[22] xts_0.11-2 jpeg_0.1-8 waterfalls_0.1.2
[25] colorspace_1.3-2 blob_1.1.1 dplyr_0.7.8
[28] rgdal_1.3-6 tcltk_3.4.4 callr_3.2.0
[31] crayon_1.3.4 RCurl_1.95-4.11 jsonlite_1.6
[34] hexbin_1.27.2 roxygen2_6.1.1 bindr_0.1.1
[37] zoo_1.8-4 glue_1.3.0 gtable_0.2.0
[40] DEoptimR_1.0-8 abind_1.4-5 scales_1.0.0
[43] padr_0.5.0 mvtnorm_1.0-7 DBI_1.0.0
[46] Rcpp_1.0.0 plotrix_3.7-4 xtable_1.8-3
[49] foreign_0.8-69 bit_1.1-14 mapproj_1.2.6
[52] dotCall64_0.9-5.2 RJDBC_0.2-7.1 htmlwidgets_1.3
[55] httr_1.4.0 RColorBrewer_1.1-2 geosphere_1.5-7
[58] pkgconfig_2.0.2 XML_3.98-1.16 rJava_0.9-10
[61] dbplyr_1.2.2 RJSONIO_1.3-1.1 tidyselect_0.2.5
[64] rlang_0.3.4 reshape2_1.4.3 later_0.7.5
[67] munsell_0.5.0 cellranger_1.1.0 tools_3.4.4
[70] cli_1.0.1 xgboost_0.71.2 moments_0.14
[73] RSQLite_2.1.1 english_1.2-3 ggmap_2.6.1
[76] ggridges_0.5.1 aws.s3_0.3.12 stringr_1.3.1
[79] processx_3.3.0 bit64_0.9-7 zip_2.0.2
[82] robustbase_0.93-3 purrr_0.2.5 ncdf4_1.16.1
[85] RgoogleMaps_1.4.3 nlme_3.1-131 mime_0.6
[88] xml2_1.2.0 compiler_3.4.4 rstudioapi_0.10
[91] png_0.1-7 ggjoy_0.4.1 RPostgreSQL_0.6-2
[94] tibble_2.1.1 stringi_1.2.4 ps_1.3.0
[97] desc_1.2.0 fields_9.6 lattice_0.20-35
[100] Matrix_1.2-12 commonmark_1.6 shinyjs_1.0
[103] stringdist_0.9.5.1 pillar_1.3.1 bitops_1.0-6
[106] maptools_0.9-4 grImport_0.9-2 raster_2.8-4
[109] httpuv_1.4.5 R6_2.4.0 latticeExtra_0.6-28
[112] promises_1.0.1 gridExtra_2.3 openair_2.6-5
[115] codetools_0.2-15 boot_1.3-20 MASS_7.3-49
[118] gtools_3.5.0 assertthat_0.2.0 proto_1.0.0
[121] rprojroot_1.3-2 rjson_0.2.18 shinyWidgets_0.4.4
[124] withr_2.1.2 mgcv_1.8-23 parallel_3.4.4
[127] hms_0.4.2 grid_3.4.4 timeDate_3043.102
[130] tidyr_0.8.3 git2r_0.25.2 shiny_1.2.0
[133] lubridate_1.7.4 base64enc_0.1-3 dygraphs_1.1.1.6
`